Staging: rt{2860,2870}sta: Use request_firmware() to load firmware

When originally introduced into staging, these drivers had custom
firmware-loading code which checked a version number and CRC at the
end of each blob.  This reintroduces those checks, using crc-ccitt
instead of custom code.

The removed firmware will be added to the linux-firmware.git
repository.

Based on work by Darren Salt <linux@youmustbejoking.demon.co.uk>.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Tested-By: Darren Salt <linux@youmustbejoking.demon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>