Import the N1SDP sensor library

N1SDP sensor library has been moved out from SCP code base to
board-firmware. SCP_N1SDP_SENSOR_LIB_PATH variable is used to
export path to sensor.a during SCP build.

Signed-off-by: sahil <sahil@arm.com>
Change-Id: I6dd619a9321dc5ba82e77c7a97bb6f3b028926b8