fix(fvp): fix fvp_cpu_standby() function
fix(fvp): fix fvp_cpu_standby() function

The latest FVP model fix which correctly checks if IRQs
are enabled in current exception level, is causing TFTF
tests to hang.
This patch adds setting SCR_EL3.I and SCR_EL3.F bits in
'fvp_cpu_standby()' function to allow CPU to exit from WFI.

Signed-off-by: Alexei Fedorov <c822f9d283009ea22aff7123d9d948b6c6849e25@arm.com>
Change-Id: Iceec1e9dbd805803d370ecdb10e04ad135d6b3aa

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware