usb: dwc3: Add frame length adjustment quirk

[backport from linux commit db2be4e9e30c6e43e48c5749d3fc74cee0a6bbb3]

Add adjust_frame_length_quirk for writing to fladj register
which adjusts (micro)frame length to value provided by
"snps,quirk-frame-length-adjustment" property thus avoiding
USB 2.0 devices to time-out over a longer run

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>