optee-os: Refresh GCC 10 patches

The original fix for compiling with GCC 10 had to be reverted because it
failed on older versions. Upstream resolved this and re-instituted the
fix, so backport that patch series

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>