USB: dwc3-msm: Add support for 24MHz utmi clock

For ref clk based SOF/ITP generation, utmi clock needs to be set
to frequencies like 19.2MHz, 24MHz etc. Hence add support for
setting utmi clock to 24MHz.

Change-Id: Ia64eaa5320846ab219c516f43e6dcdf0fb05eb89
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>