[nvptx] Fix printing of 128-bit constant

[nvptx] Fix printing of 128-bit constant

Currently, for this code from c-c++-common/spec-barrier-1.c:
...
__int128 g = 9;
...
we generate:
...
// BEGIN GLOBAL VAR DEF: g
.visible .global .align 8 .u64 g[2] = { 9, 9 };
...
and consequently the test-case fails in execution.

The problem is caused by a shift in nvptx_assemble_value:
...
      val >>= part * BITS_PER_UNIT;
...
where the shift amount is equal to the number of bits in val, which is
undefined behaviour.

Fix this by detecting the situation and setting val to 0.

Tested on nvptx.

gcc/ChangeLog:

	PR target/97004
	* config/nvptx/nvptx.c (nvptx_assemble_value): Handle shift by
	number of bits in shift operand.