USB: msm: Add support for CDC-ACM composition

Default USB composition uses proprietary serial for providing modem
functionality. Add support for CDC-ACM as well to USB supported
functions list which will help users include either proprietary serial
or CDC-ACM into USB composition.

User can enable CDC-ACM in default composition by including the acm
into init script.

Change-Id: Iac3cb5434c72003f61d5877ca2fddef7e16b76bd
CRs-fixed: 324827
Signed-off-by: Anji jonnala <anjir@codeaurora.org>