drm radeon: Return -EINVAL on wrong pm sysfs access
drm radeon: Return -EINVAL on wrong pm sysfs access

Throw an error if someone tries to fill this with
wrong data, instead of simply ignoring the input.
Now you get:

echo hello >/sys/../power_method
-bash: echo: write error: Invalid argument

Signed-off-by: Thomas Renninger <dc31099191a1a231a41b126c85d59916cd0f555f@suse.de>
CC: 51491341ca073a406db997440d5edb170930fcee@amd.com
CC: e29a046d56d20477d35c94c7163db1056870c39f@lists.freedesktop.org
Reviewed-by: Alex Deucher <bf84f557a1e54fd62cd73c6847f7d9df60e9fbef@gmail.com>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas