xtensa: reorganize SR referencing

- reference SRs by names where possible, not by numbers;
- get rid of __stringify around SR names where possible;
- remove unneeded SR names from asm/regs.h;
- add SREG_ prefix to remaining SR names;

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/kernel/irq.c b/arch/xtensa/kernel/irq.c
index 98e77c3..a6ce3e5 100644
--- a/arch/xtensa/kernel/irq.c
+++ b/arch/xtensa/kernel/irq.c
@@ -72,13 +72,13 @@
 static void xtensa_irq_mask(struct irq_data *d)
 {
 	cached_irq_mask &= ~(1 << d->irq);
-	set_sr (cached_irq_mask, INTENABLE);
+	set_sr (cached_irq_mask, intenable);
 }
 
 static void xtensa_irq_unmask(struct irq_data *d)
 {
 	cached_irq_mask |= 1 << d->irq;
-	set_sr (cached_irq_mask, INTENABLE);
+	set_sr (cached_irq_mask, intenable);
 }
 
 static void xtensa_irq_enable(struct irq_data *d)
@@ -95,7 +95,7 @@
 
 static void xtensa_irq_ack(struct irq_data *d)
 {
-	set_sr(1 << d->irq, INTCLEAR);
+	set_sr(1 << d->irq, intclear);
 }
 
 static int xtensa_irq_retrigger(struct irq_data *d)