test_firmware: add simple firmware firmware test library

We'll expland on this later, for now just add basic module checker.
While at it, move this all to use /bin/bash as we'll have much more
flexibility with it.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>