pinctrl: set unit for debounce time pinconfig to usec

Currently the debounce time pinconfig option uses an unspecified
"time units" unit. As pinconfig options should use SI units and a
real unit is also necessary for generic dt bindings, change it
to usec. Currently no driver is using the generic pinconfig option
for this, so the unit change is safe to do.

Change-Id: I6340ec8d4406868fbc4dcb9e941762bc57b7b86d
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Git-commit: 256aeb648741bf095e884793862d3dfa6b1c1fb5
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>