Staging: rt28xx: Make PCI_{MAP,UNMAP}_SINGLE type-safe

To avoid recurrence of bugs such as <http://bugs.debian.org/575726

>,
change the type of the first parameter to linux_pci_{map,unmap}_single()
from void * to struct rt_rtmp_adapter *.  Also do not define the macros
PCI_{MAP,UNMAP}_SINGLE() when building the rt2870sta driver; they are
not used and if they were that would be a bug.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>,
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>