usb: dwc2: Fix interval type issue

[ Upstream commit 12814a3f8f9b247531d7863170cc82b3fe4218fd ]

The maximum value that unsigned char can hold is 255, meanwhile
the maximum value of interval is  2^(bIntervalMax-1)=2^15.

Signed-off-by: Grigor Tovmasyan <tovmasya@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>