clk: qcom: Add missing freq for usb30_master_clk on 8998

The usb30_master_clk supports a 60Mhz frequency, but that is missing from
the table of supported frequencies.  Add it.

Fixes: b5f5f525 (clk: qcom: Add MSM8998 Global Clock Control (GCC) driver)
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>