Staging: fbtft: Fix reset assertion when using gpio descriptor

Typically gpiod_set_value calls would assert the reset line and
then release it using the symantics of:
	gpiod_set_value(par->gpio.reset, 0);
	... delay
	gpiod_set_value(par->gpio.reset, 1);
And the gpio binding would specify the polarity.

Prior to conversion to gpiod calls the polarity in the DT
was ignored and assumed to be active low. Fix it so that
DT polarity is respected.

Fixes: c440eee1 ("Staging: fbtft: Switch to the gpio descriptor interface")
Reviewed-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Tested-by: Jan Sebastian Götte <linux@jaseg.net>
Signed-off-by: Phil Reid <preid@electromag.com.au>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1563236677-5045-3-git-send-email-preid@electromag.com.au


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>