msm: kgsl: fix casting in GPUMEM ioctls

Make downcasts from 64 bit addresses and sizes match the
ioctl definitions, unsigned long and size_t, rather than
unsigned int. This allows these ioctls to work with
64 bit GPU addresses if the calling process is also 64 bit.

Change-Id: I4e1772eca3715ccaa92f49197dccb96229cb07ca
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>