firmware_loader: Expand Firmware upload error codes with firmware invalid error

No error code are available to signal an invalid firmware content.
Drivers that can check the firmware content validity can not return this
specific failure to the user-space

Expand the firmware error code with an additional code:
- "firmware invalid" code which can be used when the provided firmware
  is invalid

Sync lib/test_firmware.c file accordingly.

Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231122-feature_firmware_error_code-v3-1-04ec753afb71@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>