npcm7xx-igps: Make it possible to set HOST_IF Some platforms want to use eSPI instead of LPC, make it possible to change this value. Tested: Verified that the build output of LPC systems reflects the LPC value and eSPI the eSPI value. Google-Bug-Id: 344688999 Change-Id: Ia95f76455fa909c85b0a02f76a73484428f02b5a Signed-off-by: William A. Kennington III <wak@google.com>