firewire: add missing MODULE_DESCRIPTION() to test modules

Fix the 'make W=1' warnings:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/firewire/uapi-test.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/firewire/packet-serdes-test.o

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240523-md-firewire-uapi-test-v1-1-6be5adcc3aed@quicinc.com


Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>