sparc64: Fix bootup regressions on some Kconfig combinations.

The system call tracing bug fix mentioned in the Fixes tag
below increased the amount of assembler code in the sequence
of assembler files included by head_64.S

This caused to total set of code to exceed 0x4000 bytes in
size, which overflows the expression in head_64.S that works
to place swapper_tsb at address 0x408000.

When this is violated, the TSB is not properly aligned, and
also the trap table is not aligned properly either.  All of
this together results in failed boots.

So, do two things:

1) Simplify some code by using ba,a instead of ba/nop to get
   those bytes back.

2) Add a linker script assertion to make sure that if this
   happens again the build will fail.

Fixes: 1a40b95374 ("sparc: Fix system call tracing register handling.")
Reported-by: Meelis Roos <mroos@linux.ee>
Reported-by: Joerg Abraham <joerg.abraham@nokia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/head_64.S

@@ -466,9 +466,8 @@ sun4v_chip_type:
 	subcc	%g3, 1, %g3
 	bne,pt	%xcc, 41b
 	add	%g1, 1, %g1
-	mov	SUN4V_CHIP_SPARC64X, %g4
 	ba,pt	%xcc, 5f
-	nop
+	 mov	SUN4V_CHIP_SPARC64X, %g4
 
 49:
 	mov	SUN4V_CHIP_UNKNOWN, %g4
@@ -553,8 +552,7 @@ sun4u_init:
 	stxa		%g0, [%g7] ASI_DMMU
 	membar	#Sync
 
-	ba,pt		%xcc, sun4u_continue
-	 nop
+	ba,a,pt		%xcc, sun4u_continue
 
 sun4v_init:
 	/* Set ctx 0 */
@@ -565,14 +563,12 @@ sun4v_init:
 	mov		SECONDARY_CONTEXT, %g7
 	stxa		%g0, [%g7] ASI_MMU
 	membar		#Sync
-	ba,pt		%xcc, niagara_tlb_fixup
-	 nop
+	ba,a,pt		%xcc, niagara_tlb_fixup
 
 sun4u_continue:
 	BRANCH_IF_ANY_CHEETAH(g1, g7, cheetah_tlb_fixup)
 
-	ba,pt	%xcc, spitfire_tlb_fixup
-	 nop
+	ba,a,pt	%xcc, spitfire_tlb_fixup
 
 niagara_tlb_fixup:
 	mov	3, %g2		/* Set TLB type to hypervisor. */
@@ -647,8 +643,7 @@ niagara_patch:
 	call	hypervisor_patch_cachetlbops
 	 nop
 
-	ba,pt	%xcc, tlb_fixup_done
-	 nop
+	ba,a,pt	%xcc, tlb_fixup_done
 
 cheetah_tlb_fixup:
 	mov	2, %g2		/* Set TLB type to cheetah+. */
@@ -667,8 +662,7 @@ cheetah_tlb_fixup:
 	call	cheetah_patch_cachetlbops
 	 nop
 
-	ba,pt	%xcc, tlb_fixup_done
-	 nop
+	ba,a,pt	%xcc, tlb_fixup_done
 
 spitfire_tlb_fixup:
 	/* Set TLB type to spitfire. */
@@ -782,8 +776,7 @@ setup_trap_table:
 	call	%o1
 	 add	%sp, (2047 + 128), %o0
 
-	ba,pt	%xcc, 2f
-	 nop
+	ba,a,pt	%xcc, 2f
 
 1:	sethi	%hi(sparc64_ttable_tl0), %o0
 	set	prom_set_trap_table_name, %g2
@@ -822,8 +815,7 @@ setup_trap_table:
 
 	BRANCH_IF_ANY_CHEETAH(o2, o3, 1f)
 
-	ba,pt	%xcc, 2f
-	 nop
+	ba,a,pt	%xcc, 2f
 
 	/* Disable STICK_INT interrupts. */
 1: