fix(st): enable RTC clock before accessing nv counter

The plat_get_nv_ctr() retrieves the non-volatile counter value from
TAMP_COUNTR register in RTCTAMP peripheral. The clock needs to be
enabled before accessing it.

Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
Change-Id: I2e9fc2c7ac516d6f8624cc6c9d442ee85629bf9a
1 file changed