testsuite: make mve_intrinsic_type_overloads-int.c libc-agnostic

Glibc defines int32_t as 'int' while newlib defines it as 'long int'.

Although these correspond to the same size, g++ complains when using the
'wrong' version:
  invalid conversion from 'long int*' to 'int32_t*' {aka 'int*'} [-fpermissive]
or
  invalid conversion from 'int*' to 'int32_t*' {aka 'long int*'} [-fpermissive]

when calling vst1q(int32*, int32x4_t) with a first parameter of type
'long int *' (resp. 'int *')

To make this test pass with any type of toolchain, this patch defines
'word_type' according to which libc is in use.

2023-05-23  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/testsuite/
	* gcc.target/arm/mve/intrinsics/mve_intrinsic_type_overloads-int.c:
	Support both definitions of int32_t.