kbuild: rust_is_available: remove -v option

The -v option is passed when this script is invoked from Makefile,
but not when invoked from Kconfig.

As you can see in scripts/Kconfig.include, the 'success' macro suppresses
stdout and stderr anyway, so this script does not need to be quiet.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20230109061436.3146442-1-masahiroy@kernel.org


[ Reworded prefix to match the others in the patch series. ]
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230616001631.463536-2-ojeda@kernel.org


Signed-off-by: Miguel Ojeda <ojeda@kernel.org>