video: ssd1307fb: Do not hard code active-low reset sequence

The SSD130x OLED display reset signal is active low. Now the reset
sequence is implemented in such a way that users are forced to
define reset-gpios as GPIO_ACTIVE_HIGH in DT to make the reset work.

Do not hard code the active-low sequence into the driver but instead
allow the user to specify the gpio as GPIO_ACTIVE_LOW to reflect
the real world.

Signed-off-by: Michal Vokáč <michal.vokac@ysoft.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>