staging: fbtft: Replace custom ->reset() with generic one

staging: fbtft: Replace custom ->reset() with generic one

The custom ->reset() repeats the generic one, replace it.

Note, in newer kernels the context of the function is a sleeping one,
it's fine to switch over to the sleeping functions. Keeping the reset
line asserted longer than 20 microseconds is also okay, it's an idling
state of the hardware.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210503172114.27891-5-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>