[nvptx] Split up function ref plus const

[nvptx] Split up function ref plus const

With test-case gcc.c-torture/compile/pr92231.c, we run into:
...
nvptx-as: ptxas terminated with signal 11 [Segmentation fault], core dumped^M
compiler exited with status 1
FAIL: gcc.c-torture/compile/pr92231.c   -O0  (test for excess errors)
...
due to using a function reference plus constant as operand:
...
  mov.u64 %r24,bar+4096';
...

Fix this by splitting such an insn into:
...
  mov.u64 %r24,bar';
  add.u64 %r24,%r24,4096';
...

Tested on nvptx.

gcc/ChangeLog:

	* config/nvptx/nvptx.md: Don't allow operand containing sum of
	function ref and const.