drivers/adc: update upper-half layer

drivers/adc: update upper-half layer

This commit updates the upper-half driver of ADC subsystem,
synchronizing with the latest version of NuttX. ADC drivers that
implements the lower-half can be broken with this commit, but in TizenRT
there is no lower-half driver of ADC. Thus, this commit does not cause
any harm. All credits should go to many other contributors who wrote the
original patches for NuttX. Sorry for not listing their names here.

Change-Id: I42dc6b1fa597ae74494ef635897b4bc695e1c343
[Shin: backported from the latest NuttX]
Signed-off-by: Heesub Shin <heesub.shin@samsung.com>