Staging: xgifb: Replace udelay, mdelay functions with usleep_range

This patch fixes the checkpatch.pl check:

CHECK: usleep_range is preferred over udelay.

Replace mdelay with usleep_range function too.
Add 1 millisecond to the delay time to get a
reasonable upper limit which saves one wakeup call.
Do same throughout the file.

Signed-off-by: Navya Sri Nizamkari <navyasri.tech@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>