atomisp: tidy firmware loading code a little

The FWNAME define is never used so can be removed. The option to skip firmware
loading isn't really Cherrytrail specific so remove this and complete the
merging of the two driver versions for this file.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>