libsecril-client: add support for P libsec-ril.so

libsecril-client: add support for P libsec-ril.so

 * From P onward samsung changed the socket name in libsec-ril.so from
   Multiclient to VND_Multiclient.

 * In order to not break compatibility with older RIL stack guard this
   behind TARGET_USES_VND_SECRIL.

 * This is mostly relevant when using P (or newer) prebuilt ril stack
   coupled with OSS audio hal from hw/samsung, which depends on OSS
   libsecril-client to provide connection to the RIL daemon.

Change-Id: Iab5d07f2301d33216bbdf3e18f844522e32fadce
(cherry picked from commit 6d6c0500f3139f84163eefefc8e19dcc934ef26a)