test_firmware: Fix spelling mistake "EMTPY" -> "EMPTY"

There are spelling mistakes in config show text. Fix these.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Russ Weight <russell.h.weight@intel.com>
Link: https://lore.kernel.org/r/20220928211637.62529-1-colin.i.king@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>