USB: msm_otg: Add asynchronous block reset support for USB core

To operate correctly, USB core requires to be reset clearing
any initialization settings performed by other components
e.g. bootloader during bootup.

MSM platforms support two kinds of hardware resets:
1. Conventional synchronous reset where clocks to the
blocks must be ON while issuing the reset, and
2. Asynchronous reset which requires clocks to be OFF.

Driver can determine the supported reset methodology on the
platform based on availability of alt_core_clk.

Change-Id: Ia062818ecbf4b0cec44e55f013b762d3ee51b249
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>