sunxi: f1c100s: Fix FEL registers restore

Commit 88998f77 ("arm: arm926ej-s: Add sunxi code") introduced
the ARM926 version of the code to save and restore some FEL state, to
be able to return to the BROM FEL code after the SPL has run.

However during review a change was made, that happened to mess up the
register restore part, so SCTLR and CPSR ended up with the wrong values,
breaking return to FEL.

Use the same offset that we actually save those registers to, to make
FEL booting actually work on the Lichee Pi Nano.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>