marvel: cleanup cm.mk

* gsm.mk doesn't (actually) exist, see:
https://github.com/androidarmv6/android_vendor_cm/blob/cm-11.0/config/gsm.mk
* There's no need for a custom build fingerprint

Change-Id: Ib0fc6addb27bca619afefd9463a88ef3f9499e79
board: switch to htc_msm7227_defconfig [3/3]

Change-Id: I406634dd616994479fdc72a8fae942f2897d0d99