Import the d/g/goldfish soong namespace for libwifi-hal-emu

Some devices refer to libwifi-hal-emu via

BOARD_WLAN_DEVICE := emulator

we need to import the device/generic/goldfish
namespace to link the libwifi-hal-emu symbol.

Bug: 154151802
Test: presubmit
Signed-off-by: Roman Kiryanov <rkir@google.com>
Change-Id: I68b0f9bd22e50c2a86e0dbe62abc17991581703e