efi_loader: CloseProtocol in efi_fmp_find

The CloseProtocol() boot service requires a handle as first argument.
Passing the protocol interface is incorrect.

CloseProtocol() only has an effect if called with a non-zero value for
agent_handle. HandleProtocol() uses an opaque agent_handle when invoking
OpenProtocol() (currently NULL). Therefore HandleProtocol() should be
avoided.

* Replace the LocateHandle() call by efi_search_protocol().
* Remove the CloseProtocol() call.

Fixes: 8d99026f ("efi_loader: capsule: support firmware update")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>