Revert "Add handheld_core_hardware.xml to telephony base"

Don't do this. handheld_core_hardware.xml includes feature declarations
that aren't mandatory, particularly cameras and magnetometers, but also
things like managed users. According to the CDD, these are optional.
Go back to the pre-L mechanism of including the declarations per-device
to make them accurate.
This reverts commit dccce7bb.

Conflicts:
	target/product/full_base_telephony.mk

Change-Id: I6db55082295171b78fe595e783799ee54458c4fd