mm: Fix warning comparing pointer to 0

Fix the following coccicheck warning:

./arch/alpha/mm/fault.c:193:52-53: WARNING comparing pointer to 0.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

arch/alpha/mm/fault.c

@@ -192,7 +192,7 @@ do_page_fault(unsigned long address, unsigned long mmcsr,
 
  no_context:
 	/* Are we prepared to handle this fault as an exception?  */
-	if ((fixup = search_exception_tables(regs->pc)) != 0) {
+	if (!(fixup = search_exception_tables(regs->pc)) {
 		unsigned long newpc;
 		newpc = fixup_exception(dpf_reg, fixup, regs->pc);
 		regs->pc = newpc;