pseudomodem: Shorten error enumerations in mm1.py

This CL shortens the error enumerations in mm1.py to prevent redundancy
in naming. For example,

mm1.MMCoreError.MM_CORE_ERROR_UNKNOWN

is now

mm1.MMCoreError.UNKNOWN

BUG=chromium-os:34605
TEST=pylint

Change-Id: I173fdd0d45ea5f21606380053dfc628f7bb51d45
Reviewed-on: https://gerrit.chromium.org/gerrit/37578
Reviewed-by: Thieu Le <thieule@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Ready: Arman Uguray <armansito@chromium.org>
Tested-by: Arman Uguray <armansito@chromium.org>
3 files changed