ipc: ipc_service: Inline libmetal_{setup,teardown}() for correct ordering

Currently metal_init() is called as part of libmetal_setup() which is
called after libmetal has already started being used (metal_io_init
called before). Same for metal_finish() but in reverse (metal_io_finish
called after). To fix this inline the content of libmetal_{setup,teardown}
into their one call-sites and move the init/finish calls to the correct
spot before/after all uses of the lib.

Signed-off-by: Andrew Davis <afd@ti.com>