deb-pkg: Add support for powerpc little endian

The Debian powerpc little endian architecture is called ppc64el.  This
is the default architecture used by Ubuntu for powerpc.

The below checks the kernel config to see if we are compiling little
endian and sets the Debian arch appropriately.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>