Fix sloppy PR126536 test

This test failed with

FAIL: gcc.dg/pr126536-1.c (test for excess errors)
Excess errors:
gcc.dg/pr126536-1.c:37:5: warning: overflow in conversion from 'long int' to 'int' changes value from '100000' to '-31072' [-Woverflow]
gcc.dg/pr126536-1.c:37:5: warning: empty range specified
gcc.dg/pr126536-1.c:39:5: warning: overflow in conversion from 'long int' to 'int' changes value from '200000' to '3392' [-Woverflow]
FAIL: gcc.dg/pr126536-1.c execution test

As it's obviously requiring int32plus in the argument of f.
Hence use __INT32_TYPE__ instead of int.

gcc/testsuite/
	PR testsuite/126536
	* gcc.dg/pr126536-1.c (f): Pass a as __INT32_TYPE__.

gcc/testsuite/gcc.dg/pr126536-1.c

diff --git a/gcc/testsuite/gcc.dg/pr126536-1.c b/gcc/testsuite/gcc.dg/pr126536-1.c
index 0f87015..0b97fa7 100644
--- a/gcc/testsuite/gcc.dg/pr126536-1.c
+++ b/gcc/testsuite/gcc.dg/pr126536-1.c
@@ -3,7 +3,7 @@
 volatile int v;
 
 __attribute__((noipa)) int
-f (int a)
+f (__INT32_TYPE__ a)
 {
   switch (a)
     {