dwc3-msm: Add support to pass USB GSI registers offset from device tree

On some platform, USB GSI DBL and RING related registers offset are
changed due to more number of GSI interrupter available. Hence this
change adds support to pass all USB GSI registers offset from devicetree
so different offsets for same USB GSI register on different platform
can be used.

Change-Id: I23b0e16aa8e206698a9f547b1ab837985e50505c
Signed-off-by: Mayank Rana <mrana@codeaurora.org>