[media] dib0700: Fix IR keycode handling

Fixes Fedora 14 bug: https://bugzilla.redhat.com/show_bug.cgi?id=667157

There are a few bugs at the code that generates the scancode at dib0700:
	- RC keycode is wrong (it outputs a 24 bits keycode);
	- NEC extended outputs a keycode that have endiannes issues;
	- keycode tables for NEC extended remotes need to be updated.

The last issue need to be done as we get reports, as we don't have
the complete NEC-extended keycodes at the dibcom table.

This patch fixes the first two issues.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>