drm/amdgpu: Fix unnecessary else after return in 'amdgpu_eeprom_xfer'

Fixes the following:

WARNING: else is not generally useful after a break or return
+               return -EINVAL;
+       } else {

Cc: Guchun Chen <guchun.chen@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>