ARM: stm32: Jump to ep on successful resume in PSCI suspend code

ARM: stm32: Jump to ep on successful resume in PSCI suspend code

In case the system has resumed successfully, the PSCI suspend resume
code has to jump to the 'ep' successful resume entry point code path,
otherwise the code has to jump to content of the LR register, which
points to failed resume code path.

To implement this distinction, rewrite LR register stored on stack
with 'ep' value in case of a successful resume, which is really in
every case unless some catastrophic failure occurred during suspend.

Without this change, Linux counts every resume as failed in
/sys/power/suspend_stats/fail

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>