net/mlx5: fix pre-2.40 binutils assembler error

net/mlx5: fix pre-2.40 binutils assembler error

Old binutils versions require a slightly stricter syntax for the .arch_extension
directive and fail with the extra semicolon:

/tmp/cclfMnj9.s:656: Error: unknown architectural extension `simd;'

Drop the semicolon to make it work with all supported toolchain version.

Link: https://lore.kernel.org/all/20251001163655.GA370262@ax162/
Reported-by: Paolo Abeni <pabeni@redhat.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Fixes: fd8c8216648c ("net/mlx5: Improve write-combining test reliability for ARM64 Grace CPUs")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Patrisious Haddad <phaddad@nvidia.com>
Link: https://patch.msgid.link/20251006115640.497169-1-arnd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>