Fixes commit 25173f71cd ("pm: device_runtime: Extend with synchronous
runtime PM")
Fixes compilation with gcc 4.2-based toolchain used by SOF for TGL
generation products. As seen in the error message below, that gcc
version requires braces for initialization of anonymous unions:
```
zephyr/soc/xtensa/intel_adsp/common/mem_window.c:62:
error: unknown field ‘pm_base’ specified in initializer
warning: missing braces around initializer
warning: (near initialization for ‘__device_dts_ord_66.<anonymous>’)
```
This is a well-known and recurring issue, see past example(s) in #68118
As the Zephyr build is deterministic, I could easily verify that this
commit makes zero .obj difference (when using the Zephyr SDK).
Signed-off-by: Marc Herbert <marc.herbert@intel.com>
f91d4731af