usb: dwc2: Update Core Reset programming flow.

Starting from core version 4.20a Core Reset flow is changed.
Introduced new bit in GRSTCTL register - GRSTCTL_CSFTRST_DONE.
Core Reset new programming flow steps are follow:
1. Set GRSTCTL_CSFTRST bit.
2. Wait for bit GRSTCTL_CSFTRST_DONE is set.
3. Clear GRSTCTL_CSFTRST and GRSTCTL_CSFTRST_DONE bits.

Check core version functionality separated from dwc2_get_hwparams() to
new dwc2_check_core_version() function because Core Reset flow depend
on SNPSID.

Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>