ARM: sunxi: smp: Move assembly code into a file

Move the assembly code for cluster cache enabling and resuming
into an assembly file instead of having it directly in C code.

Remove the CFLAGS because we are using the ARM directive "arch"
instead.

Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>