drm/amdgpu: Return result fix in RAS

The low level EEPROM write method, doesn't return
1, but the number of bytes written. Thus do not
compare to 1, instead, compare to greater than 0
for success.

Other cleanup: if the lower layers returned
-errno, then return that, as opposed to
overwriting the error code with one-fits-all
-EINVAL. For instance, some return -EAGAIN.

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Alexander Deucher <Alexander.Deucher@amd.com>
Cc: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Cc: Lijo Lazar <Lijo.Lazar@amd.com>
Cc: Stanley Yang <Stanley.Yang@amd.com>
Cc: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
Reviewed-by: Alexander Deucher <Alexander.Deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>