Staging: comedi: drivers.c: fix PAGE_KERNEL_NOCACHE issue

Not all arches have PAGE_KERNEL_NOCACHE, so use the "normal" PAGE_KERNEL
on those that do not have it.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>