usb: dwc3: gadget: Rename EOPF event macros to Suspend

The device event corresponding to End of Periodic Frame is only
found on older IP revisions (2.10a and prior, according to a
cursory SNPS databook search).  On revisions 2.30a and newer,
including DWC3.1, the same event value and corresponding DEVTEN
bit were repurposed to indicate that the link has gone into
suspend state (U3 or L2/L1).

EOPF events had never been enabled before in this driver, and
going forward we expect current and future DWC3-based devices
won't likely to be using such old DWC3 IP revisions either.
Hence rather than keeping the deprecated EOPF macro names let's
rename them to indicate their usage for suspend events.

Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Link: https://lore.kernel.org/r/20210428090111.3370-2-jackp@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>