[PARISC] Remove sched.h from uaccess.h on parisc

Al Viro did this for x86-64 and reduced the number of dependencies on
sched.h significantly.  We had a couple of files which were relying on
uaccess.h pulling in sched.h, so they need explicit dependencies added.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>