drivers/gpio: fix incorrect edge detection
drivers/gpio: fix incorrect edge detection

Edge detection logic in GPIO upper-half driver is completely wrong and
should be fixed.

Change-Id: I3e01a7e7a09194e188a60c3a1e553e908782fdb8
Signed-off-by: Heesub Shin <45471ea77bd08f3d26635f3f5adb40ba41250a2b@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT