sparc32: Fix thinko in previous change.

Should mask stack with 0xf not "0x15".

Noticed by Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

arch/sparc/kernel/process_32.c

@@ -526,7 +526,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 			 * Set some valid stack frames to give to the child.
 			 */
 			childstack = (struct sparc_stackf __user *)
-				(sp & ~0x15UL);
+				(sp & ~0xfUL);
 			parentstack = (struct sparc_stackf __user *)
 				regs->u_regs[UREG_FP];