powerpc/32s: get rid of CPU_FTR_601 feature

Now that 601 is exclusive from other 6xx, CPU_FTR_601 and
associated fixups are useless.

Drop this feature and use #ifdefs instead.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/ecdb7194a17dbfa01865df6a82979533adc2c70b.1566834712.git.christophe.leroy@c-s.fr

arch/powerpc/kernel/entry_32.S

@@ -777,11 +777,19 @@ fast_exception_return:
 1:	lis	r3,exc_exit_restart_end@ha
 	addi	r3,r3,exc_exit_restart_end@l
 	cmplw	r12,r3
+#if CONFIG_PPC_BOOK3S_601
+	bge	2b
+#else
 	bge	3f
+#endif
 	lis	r4,exc_exit_restart@ha
 	addi	r4,r4,exc_exit_restart@l
 	cmplw	r12,r4
+#if CONFIG_PPC_BOOK3S_601
+	blt	2b
+#else
 	blt	3f
+#endif
 	lis	r3,fee_restarts@ha
 	tophys(r3,r3)
 	lwz	r5,fee_restarts@l(r3)
@@ -800,9 +808,6 @@ fee_restarts:
 /* aargh, we don't know which trap this is */
 /* but the 601 doesn't implement the RI bit, so assume it's OK */
 3:
-BEGIN_FTR_SECTION
-	b	2b
-END_FTR_SECTION_IFSET(CPU_FTR_601)
 	li	r10,-1
 	stw	r10,_TRAP(r11)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
@@ -1270,11 +1275,19 @@ nonrecoverable:
 	lis	r10,exc_exit_restart_end@ha
 	addi	r10,r10,exc_exit_restart_end@l
 	cmplw	r12,r10
+#ifdef CONFIG_PPC_BOOK3S_601
+	bgelr
+#else
 	bge	3f
+#endif
 	lis	r11,exc_exit_restart@ha
 	addi	r11,r11,exc_exit_restart@l
 	cmplw	r12,r11
+#ifdef CONFIG_PPC_BOOK3S_601
+	bltlr
+#else
 	blt	3f
+#endif
 	lis	r10,ee_restarts@ha
 	lwz	r12,ee_restarts@l(r10)
 	addi	r12,r12,1
@@ -1283,9 +1296,6 @@ nonrecoverable:
 	blr
 3:	/* OK, we can't recover, kill this process */
 	/* but the 601 doesn't implement the RI bit, so assume it's OK */
-BEGIN_FTR_SECTION
-	blr
-END_FTR_SECTION_IFSET(CPU_FTR_601)
 	lwz	r3,_TRAP(r1)
 	andi.	r0,r3,1
 	beq	5f