drm/amdgpu: optimize timeout implemention in ras_eeprom_update_record_num

drm/amdgpu: optimize timeout implemention in ras_eeprom_update_record_num

The busy status returned by ras_eeprom_update_record_num may not be
an error, increase timeout to exclude false busy status. Also add more
comments to make the code readable.

v2: define a macro for the timeout value.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>