arm: Consistently use proper interworking function returns

arm: Consistently use proper interworking function returns

Use "bx lr", or "pop {lr}", which do proper mode switching
between thumb and arm modes. A plain "mov pc, lr" does not switch
from thumb mode to arm mode (while in arm mode, it does switch
mode for a thumb caller).

This is normally not an issue, as CONFIG_THUMB only is enabled if
the C compiler defaults to thumb; but stick to patterns that can
do mode switching if needed, for consistency.

Signed-off-by: Martin Storsjö <martin@martin.st>
(cherry picked from commit 77e6293735262b20a86b5047b77991a86cf4e9e1)

Gbp-Pq: Name 0008-arm-Consistently-use-proper-interworking-function-re.patch