gpio: qpnp-pin: Add support for MPP devices

Add mpp support to the qpnp-pin driver. MPP support allows for
additional devices to be specified in the Device Tree topology.
This support is implemented in the same driver as the GPIO
support since the address map is very close between them.
The addition of this support does not change the existing gpio
support.

Default MPP configuration can be specified in the Device Tree
using the three new bindings for mpp. Any attribute not specified
in the Device Tree will assume its default configuration.

It's also possible to configure an MPP at runtime using the
existing qpnp_pin_config() API. If a given configuration feature
is not supported by the underlying hardware pin, then that
particular request is silently dropped with no error. This allows
for gpio users to continue specifying only a subset of the full
qpnp_pin_cfg structure.

Change-Id: I2b72768647de2a371edfa05c52fc1ed776c215c0
Signed-off-by: Michael Bohan <mbohan@codeaurora.org>
3 files changed