staging: greybus: fix stack size warning with UBSAN

commit 144779ed

 upstream.

clang warns about excessive stack usage in this driver when
UBSAN is enabled:

drivers/staging/greybus/audio_topology.c:977:12: error: stack frame size of 1836 bytes in function 'gbaudio_tplg_create_widget' [-Werror,-Wframe-larger-than=]

Rework this code to no longer use compound literals for
initializing the structure in each case, but instead keep
the common bits in a preallocated constant array and copy
them as needed.

Link: https://github.com/ClangBuiltLinux/linux/issues/1535
Link: https://lore.kernel.org/r/20210103223541.2790855-1-arnd@kernel.org/
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[nathan: Address review comments from v1]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20211209195141.1165233-1-nathan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>