powerpc/64: Move set_soft_enabled() and rename

Move set_soft_enabled() from powerpc/kernel/irq.c to asm/hw_irq.c, to
encourage updates to paca->soft_enabled done via these access
function. Add "memory" clobber to hint compiler since
paca->soft_enabled memory is the target here.

Renaming it as soft_enabled_set() will make namespaces works better as
prefix than a postfix when new soft_enabled manipulation functions are
introduced.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/setup_64.c

@@ -189,7 +189,7 @@ static void __init fixup_boot_paca(void)
 	/* Allow percpu accesses to work until we setup percpu data */
 	get_paca()->data_offset = 0;
 	/* Mark interrupts disabled in PACA */
-	get_paca()->soft_enabled = IRQS_DISABLED;
+	soft_enabled_set(IRQS_DISABLED);
 }
 
 static void __init configure_exceptions(void)
@@ -352,7 +352,7 @@ void __init early_setup(unsigned long dt_ptr)
 void early_setup_secondary(void)
 {
 	/* Mark interrupts disabled in PACA */
-	get_paca()->soft_enabled = 0;
+	soft_enabled_set(IRQS_DISABLED);
 
 	/* Initialize the hash table or TLB handling */
 	early_init_mmu_secondary();