[nvptx] Fix ASM_SPEC workaround for sm_30

[nvptx] Fix ASM_SPEC workaround for sm_30

Newer versions of CUDA no longer support sm_30, and nvptx-tools as
currently doesn't handle that gracefully when verifying
( https://github.com/MentorEmbedded/nvptx-tools/issues/30 ).

There's a --no-verify work-around in place in ASM_SPEC, but that one doesn't
work when using -Wa,--verify on the command line.

Use a more robust workaround: verify using sm_35 when misa=sm_30 is specified
(either implicitly or explicitly).

Tested on nvptx.

gcc/ChangeLog:

2022-03-30  Tom de Vries  <tdevries@suse.de>

	* config/nvptx/nvptx.h (ASM_SPEC): Use "-m sm_35" for -misa=sm_30.