clk: qcom: gcc-sc7180: Add 50 MHz clock rate for SDC2

50 MHz is an incredibly common clock rate for SD cards to run at.
It's "high speed" mode in SD (not very fast these days, but it used to
be) or:
  #define HIGH_SPEED_MAX_DTR	50000000

If we don't support this then older "high speed" cards can only run at
25 MHz or at half their normal speed.  There doesn't seem to be any
reason to skip this clock rate, so add it.

Fixes: 17269568 ("clk: qcom: Add Global Clock controller (GCC) driver for SC7180")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20201210102234.2.I26dcc0cee374f5571d9929c9985f463773167e68@changeid


Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>