Remove Kernel Command Line Support for CDMA Config

Remove support for the kernel-command-line-based CDMA
modem config flag. Devices must now use the system property,
which is also set at OS compile time and is available before
telephony. Since there's no drawback, and kernel command line
flags are not the right place for this, good riddance.

These APIs were marked @UnsupportedAppUsage; however, the
API to read the command line had zero usage, and the API to
retrieve the CDMA capability had a single app usage with a
very small installed base, so presumably it's legacy hardware.

Bug: 138225216
Test: compilation (no functional change)
Change-Id: Iac7a23056553465e1d05299df7323daf89fbfd66