pinconf-generic: add BIAS_BUS_HOLD pinconf

Add a new PIN_CONFIG_BIAS_BUS_HOLD pin configuration for a bus holder
pin mode (also known as bus keeper, or repeater). This is a weak latch
which drives the last value on a tristate bus. Another device on the bus
can drive the bus high or low before going tristate to change the value
driven by the pin.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Git-commit: a2df4269cad79635201587c5c5404f0b1cb
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git


Change-Id: I9d2aa7a76c7f24f88cf67896909bc57860ceb015
Signed-off-by: Hanumant Singh <hanumant@codeaurora.org>