staging: fwserial: (coding style) Turning every "unsigned" into "unsigned int"

Coding-style-only modifications to remove every warning saying:
WARNING: Prefer 'unsigned int' to bare use of 'unsigned'

Compiled against revision "next-20160327".

(checkpatch.pl was updated to treat "UNSPECIFIED_INT" warnings
 as of commit a1ce18e4 )

Signed-off-by: Dominique van den Broeck <domdevlin@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>