Fixes gcc '-Wunused-but-set-variable' warning:

sound/pci/lx6464es/lx_core.c: In function 'lx_interrupt_handle_async_events':
sound/pci/lx6464es/lx_core.c:990:6: warning:
 variable 'urun_mask' set but not used [-Wunused-but-set-variable]
sound/pci/lx6464es/lx_core.c:989:6: warning:
 variable 'orun_mask' set but not used [-Wunused-but-set-variable]

They are never used, so can be removed.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>