selftests: firmware: Fix it to do root uid check and skip

[ Upstream commit c65e4153 ]

firmware attempts to load test modules that require root access
and fail. Fix it to check for root uid and exit with skip code
instead.

Before this fix:

selftests: firmware: fw_run_tests.sh
modprobe: ERROR: could not insert 'test_firmware': Operation not permitted
You must have the following enabled in your kernel:
CONFIG_TEST_FIRMWARE=y
CONFIG_FW_LOADER=y
CONFIG_FW_LOADER_USER_HELPER=y
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
not ok 1 selftests: firmware: fw_run_tests.sh # SKIP

With this fix:

selftests: firmware: fw_run_tests.sh
skip all tests: must be run as root
not ok 1 selftests: firmware: fw_run_tests.sh # SKIP

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Reviwed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>