stm32mp: cosmetic: Update of bsec driver

Remove unnecessary return in stm32mp_bsec_write_lock and replace tab
by space for plat_auto opts.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>