rt2x00: rt2x00mmio: use rt2x00mmio prefix in function names

The functions in the rt2x00mmio module has been
moved from the rt2x00pci module. Each function
uses the rt2x00pci prefix which is a bit confusing.
Use the r2x000mmio prefix for each function to make
it consistent with the module name.

The renamed functions are used by several modules,
and updating the names in all of them would result
in a big patch. In order to keep the patch simple,
add compatibility defines for the old function
names. This allows to update the names in each
module separately. After each module is updated,
the defines can be removed.

The patch contains no functional changes.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>