drivers/lcd: ssd1306: fix memory corruption caused by ssd1306_getrun(). ...

drivers/lcd: ssd1306: fix memory corruption caused by ssd1306_getrun().  ssd1306_getrun was writing one extra byte (with value 0) past target buffer when pixlen is multiple of 8. When pixlen was not multiple of 8, last byte of buffer was fully cleared, instead of modifying only the (pixlen % 8) bits of last byte.