ARM platforms: Initialize cntfrq for BL1 Firmware update

Currenly the CNTFRQ register and system timer is initialized in BL31 for
use by the normal world. During firmware update, the NS-BL1 or NS-BL2U
may need to access the system timer. Hence this patch duplicates the
CNTFRQ and system timer initialization in BL1 as well.

Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Change-Id: I1ede78b4ae64080fb418cb93f3e48b26d7b724dc
diff --git a/docs/firmware-design.rst b/docs/firmware-design.rst
index e3500c2..8aa7622 100644
--- a/docs/firmware-design.rst
+++ b/docs/firmware-design.rst
@@ -306,6 +306,8 @@
 -  If the BL1 dynamic configuration file, ``TB_FW_CONFIG``, is available, then
    load it to the platform defined address and make it available to BL2 via
    ``arg0``.
+-  Configure the system timer and program the `CNTFRQ_EL0` for use by NS-BL1U
+   and NS-BL2U firmware update images.
 
 Firmware Update detection and execution
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^