armv8: move low-level assembly functions into function-sections

armv8: move low-level assembly functions into function-sections

TPL builds today don't need to call into firmware or set up the MMU
(if this changes, it should be controlled through a config option
whether to include this or not), but include the needed support code
for this anyway.  By moving these unused low-level functions into
seperate function-sections, the linker can garbage-collect the unused
sections.

Note that (if DM support is enabled), there will be a call to the
cache-flushing code from alloc_priv(...) in drivers/core/device.c.
This then add 52 bytes of binary size (an increase from 20589 to 20641
bytes) compared to completely removing this code.

Even for a feature-rich TPL (including DM support as for the RK3368),
this equates to a size difference of significantly more than 10% in
TPL binary size.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>