NFC: Set enable gpio to low

If ese gpio is not present on target, and we disable
NFC then enable gpio should be set to LOW.

Negative gpio value is invalid case, we should avoid
gpio free for error scenario.

Change-Id: I87c890bbb66ee683129f062a2aa4c8d95d5c93ee
Signed-off-by: Gaurav Singhal <gsinghal@codeaurora.org>