gpio: qpnp-gpio: Rename driver to qpnp-pin

Since QPNP PMICs also include support for MPP, and since we
intend to support MPPs in the same code base, it's not
appropriate to limit this the scope of this driver to 'gpio'.
Change the driver name to 'pin' since it more accurately
describes the potential for this driver.

Also update the Device Tree include files for the name changes.
Remove a superflous 'gpio-pin' definition in the msmcopper
specific include file, since such configuration shall never
change. This binding should be defined in the PMIC specific
include only.

Change-Id: Id1d6407039908e3cf44dfc19af71f0cdc7aff8e6
Signed-off-by: Michael Bohan <mbohan@codeaurora.org>