1. Introduce the "struct pxa27x_keypad" structure for driver specific
    information, such as "struct clk", generated matrix key codes and
    so on

 2. Use KEY() macro to define matrix keys, instead of original 8x8 map
    this makes definition easier with keypad where keys are sparse

 3. Keep a generated array in "struct pxa27x_keypad" for fast lookup

 4. Separate the matrix scan into a dedicated function for readability
    and report only those keys whose state has been changed, instead
    of report all states

 5. Make use of KPAS to decide the faster path if only one key has been
    detected
Signed-off-by: NEric Miao <eric.miao@marvell.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

The pin configurations will slowly be moved to the board specific code
at initialization thus to make the driver more generic.
Signed-off-by: NEric Miao <eric.miao@marvell.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

The controller should really be called keypad, and also align
the naming of functions and structures to use "pxa27x_keypad"
as prefix, instead of "pxakbd".
Signed-off-by: NEric Miao <eric.miao@marvell.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

Signed-off-by: NRodolfo Giometti <giometti@enneenne.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>