icorem6[_rqs]: Move the spl code common

SPL code for icorem6 and icorem6_rqs are same, so
move them in common area.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Matteo Lisi <matteo.lisi@engicam.com>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>