cosmetic: rename mgcp_ep.c/h to mgcp_endp.c/h

The short term of endpoint has always been "endp" througout the whole
project and not "ep".

- rename mcgp_ep.c to mgcp_endp.c

- rename mgcp_ep.h to mgcp_endp.h

Change-Id: Id52047bb2d0407655ac272c858ed3412b8ae9e6d
13 files changed