serial: msm_geni_serial: Decide UART sampling rate based on config

Clock divider needs to get doubled for QUP HW version greater
than 2.5.0 as sampling rate is half. As earlycon can't have HW
version awareness, decision is taken based on the configuration.

Change-Id: I639b8b5bff1d3b897d6d202501708a195e0dac31
Signed-off-by: Mitul Golani <mgolani@codeaurora.org>