drivers: firmware: ti_sci: Get SCI revision only if TIFS/SYSFW is up

drivers: firmware: ti_sci: Get SCI revision only if TIFS/SYSFW is up

When setting up boot media to load the TIFS binary in legacy boot flow
(followed by J721E), get_timer() is called which calls dm_timer_init()
which then gets the tick-timer: mcu_timer0. mcu_timer0 uses k3_clks
(clock controller) and k3_pds (power controller) from the dmsc node that
forces probe of the ti_sci driver of TIFS that hasn't been loaded yet!
Running ti_sci_cmd_get_revision from the probe leads to panic since no
TIFS and board config binaries have been loaded yet. Resolve this by
moving ti_sci_cmd_get_revision to ti_sci_get_handle_from_sysfw as a
common point of invocation for both legacy and combined boot flows.

Before doing this, it is important to go through whether any sync points
exist where revision is needed before ti_sci_get_handle_from_sysfw is
invoked. Going through the code along with boot tests on both flows
ensures that there are none.

Signed-off-by: Neha Malcom Francis <n-francis@ti.com>