fix(st-ddr): bad refresh update level toggle sequence

wait_refresh_update_done_ack() must toggle RFSHCTL3_REFRESH_UPDATE_LEVEL
bit at each call to follow the recommended procedure.
Fix action and loop condition.

Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@foss.st.com>
Change-Id: Iacf1e92a1ddaf2ab10e4f3a873be6ad1d3576e5f
1 file changed