parisc: Fix wrong comment regarding first pmd entry flags

The first pmd entry is marked with PxD_FLAG_ATTACHED instead of
_PAGE_GATEWAY.

Signed-off-by: Helge Deller <[e-mail]>

arch/parisc/include/asm/pgalloc.h

···
 				        PxD_FLAG_VALID | 
 					PxD_FLAG_ATTACHED) 
 			+ (__u32)(__pa((unsigned long)pgd) >> PxD_VALUE_SHIFT));
-		/* The first pmd entry also is marked with _PAGE_GATEWAY as
+		/* The first pmd entry also is marked with PxD_FLAG_ATTACHED as
 		 * a signal that this pmd may not be freed */
 		__pgd_val_set(*pgd, PxD_FLAG_ATTACHED);
 #endif