drivers: staging: greybus: audio_manager_sysfs.c: Fixed CHECK for brace issue

Added braces to else and else if statements where checkpatch complained.

Signed-off-by: Chase Metzger <chasemetzger15@gmail.com>
Reviewed-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>