libbt-qcom: Allow building without proprietary bits

Change-Id: I1a123e84064e441e7b4d3bf3437fa655f38f38c2
libbt: Fix case where SoC type is not set

Change-Id: Idbd953f2a17c426efb24b436b1933d4170732e54
Remove QCOM platform check from top makefile

This is redundant, bt-vendor already checks for BOARD_HAVE_BLUETOOTH_QCOM

Change-Id: I8f841418ff6a196734587d17b8bf8d640cc128c4