drm/amdgpu: remove unnecessary reading for epprom header

If the number of badpage records exceed the threshold, driver has
updated both epprom header and control->tbl_hdr.header before gpu reset,
therefore GPU recovery thread no need to read epprom header directly.

v2: merge amdgpu_ras_check_err_threshold into amdgpu_ras_eeprom_check_err_threshold

Signed-off-by: Dennis Li <Dennis.Li@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>