usb: mtu3: add optional clock xhci_ck and frmcnt_ck

Add optional clock 'xhci_ck' which is usually the same as sys_ck, but
some SoC use two separated clocks when the controller supports dual
role mode;
Add optional clock 'frmcnt_ck' used on 4nm or advanced process SoC.

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20230417025203.18097-7-chunfeng.yun@mediatek.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>