To clarify the code a bit, introduce a helper function to set/clear
the GRP2WR bit in the CFG1 register. This bit selects which group of
registers are used for the registers that share the same I/O addresses.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com> Reviewed-by: Ian Abbott <abbotti@mev.co.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>