msm7x30: do not build board-msm7x30.c

Change-Id: I8bee9ffbf598329d54a8d74b0783833ade762d2f
HTC/Kconfig: use MIPI for > 7x30

 * 7x30 will define theirs in the board's Kconfig

Change-Id: I791c53f395150a2ac2f5d98a9e7e847a31228565