nrf51: Add definitions for GPIOTE, the GPIO Tasks and Events.
nrf51: Add definitions for GPIOTE, the GPIO Tasks and Events.

Updated to use parameters for GPIOTE_OUT, GPIOTE_IN, and GPIOTE_CONFIG
Updated with NRF51_GPIOTE_IN_COUNT to remove the magic number.

BUG=chrome-os-partner:34477
BRANCH=none
TEST=Configured IN[] events and PORT events and checked that they triggered
events and wrote to the console.

Signed-off-by: Myles Watson <5fb4cec39c2b8f78857f7951c3db11d932932621@chromium.org>

Change-Id: I2021ecbee67c39571f277c97082378dce4de024f
Reviewed-on: https://chromium-review.googlesource.com/234289
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Tested-by: Myles Watson <5fb4cec39c2b8f78857f7951c3db11d932932621@chromium.org>
Reviewed-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>
Commit-Queue: Myles Watson <5fb4cec39c2b8f78857f7951c3db11d932932621@chromium.org>

fourier49/BIZ_EC,fourier49/BZ_DEV_EC,fourier49/BZ_DEV_EC,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,coreboot/chrome-ec,md5555/ec,eatbyte/chromium-ec,coreboot/chrome-ec,fourier49/BIZ_EC,mtk09422/chromiumos-platform-ec,md5555/ec,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,mtk09422/chromiumos-platform-ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,fourier49/BIZ_EC,fourier49/BZ_DEV_EC,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,coreboot/chrome-ec,eatbyte/chromium-ec