Use the gpios instead of gpio suffix that is mandated by the binding.
This dtbs_check warning is fixed now:

  touchscreen@5c: Unevaluated properties are not allowed ('reset-gpio' was unexpected)

The reset signal worked correctly as both the "gpio" and "gpios" suffixes
are actually allowed by the gpiolib.
Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>