libmfx.pc: add additional libraries required to link to libmfx
libmfx.pc: add additional libraries required to link to libmfx

In order for other projects to link to libmfx, -lstdc++ and
-ldl are required.  Thus, specify this in the package config
spec file.

Signed-off-by: U. Artie Eoff <32aece0d55055227b44d04b7d0051cf3d04ee871@intel.com>

Intel-Media-SDK/MediaSDK,Intel-Media-SDK/MediaSDK,Intel-Media-SDK/MediaSDK,Intel-Media-SDK/MediaSDK,Intel-Media-SDK/MediaSDK