nrf51: Copy the keyboard_raw.c implementation from stm32.
nrf51: Copy the keyboard_raw.c implementation from stm32.

BUG=chrome-os-partner:34477
BRANCH=none
TEST=make buildall -j

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

Change-Id: I2ad095a499e960e4b2929792708a563e5b1e1922
Reviewed-on: https://chromium-review.googlesource.com/234393
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Tested-by: Myles Watson <5fb4cec39c2b8f78857f7951c3db11d932932621@chromium.org>
Commit-Queue: Myles Watson <5fb4cec39c2b8f78857f7951c3db11d932932621@chromium.org>

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