sparc32: fix PAGE_SIZE definition

Use _AC() in definition of PAGE_SIZE so the same definition
can be used in C and assembler.
Also use PAGE_SIZE in definition of THREAD_SIZE.

This commit kill the following comment:

    "I have my suspicions... -DaveM"

I did not find any clue what this referred to anyway.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc/include/asm/thread_info_32.h b/arch/sparc/include/asm/thread_info_32.h
index fa57532..e418690 100644
--- a/arch/sparc/include/asm/thread_info_32.h
+++ b/arch/sparc/include/asm/thread_info_32.h
@@ -95,7 +95,7 @@
  * Observe the order of get_free_pages() in alloc_thread_info_node().
  * The sun4 has 8K stack too, because it's short on memory, and 16K is a waste.
  */
-#define THREAD_SIZE		8192
+#define THREAD_SIZE		(2 * PAGE_SIZE)
 
 /*
  * Offsets in thread_info structure, used in assembly code