sunxi: fel: drop redundant "control register" save/restore

sunxi: fel: drop redundant "control register" save/restore

For some reasons shrouded in mystery, the code saving the FEL state was
saving the SCTLR register twice, with the second copy trying to justify
itself by using its ancient "control register" alias name.

Drop the redundant second copy, both from the fel_stash data structure,
and also the code saving and restoring it.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Tested-by: Samuel Holland <samuel@sholland.org>