Revert "ARM: dts: remove modem node in sda845 RB3 HW"

This reverts commit 5e3adcf9.
Mode issue on RB3 fixed by replace modem flavor in META,
not need to disable modem node in AP.

Change-Id: I4bda28bfb70670154390ab55a6532865ce7c6a5c
Signed-off-by: Guang Yang <guyang@codeaurora.org>