sparc64: Do not save/restore interrupts in get_new_mmu_context()

get_new_mmu_context() is always called with interrupts disabled.
So it's possible to do this micro optimization.

(Also fix the comment to switch_mm, which is called in both cases)

Signed-off-by: Kirill Tkhai <tkhai@yandex.ru>
CC: David Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/mm/init_64.c

@@ -681,10 +681,9 @@ void get_new_mmu_context(struct mm_struct *mm)
 {
 	unsigned long ctx, new_ctx;
 	unsigned long orig_pgsz_bits;
-	unsigned long flags;
 	int new_version;
 
-	spin_lock_irqsave(&ctx_alloc_lock, flags);
+	spin_lock(&ctx_alloc_lock);
 	orig_pgsz_bits = (mm->context.sparc64_ctx_val & CTX_PGSZ_MASK);
 	ctx = (tlb_context_cache + 1) & CTX_NR_MASK;
 	new_ctx = find_next_zero_bit(mmu_context_bmap, 1 << CTX_NR_BITS, ctx);
@@ -720,7 +719,7 @@ void get_new_mmu_context(struct mm_struct *mm)
 out:
 	tlb_context_cache = new_ctx;
 	mm->context.sparc64_ctx_val = new_ctx | orig_pgsz_bits;
-	spin_unlock_irqrestore(&ctx_alloc_lock, flags);
+	spin_unlock(&ctx_alloc_lock);
 
 	if (unlikely(new_version))
 		smp_new_mmu_context_version();