ARM: dts: msm: Remove unused dtsi flag for MSM8920/MSM8940

Current code does not use "qcom,enable-hsusb-bam-on-boot" flag
for selecting BAM on bootup. Now USB_BAM is enabled only for
BAM2BAM function. Hence remove unused flag and enable BAM
whenever BAM2BAM function is present in the composition.

Change-Id: I831d6aa5af69d1cade561fd149b5a323f2888b05
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>