wifi: ath11k: allow missing memory-regions

On SC7280 platforms which are running with TrustZone, it is not
necessary to manually map the memory regions used by the wifi hardware.
However, ath11k will currently fail to load unless both memory regions
are specified.

This breaks wifi on the rb3gen2 which only specifies the firmware memory
region and does not use the CE region.

Adjust the order of operations in ath11k_ahb_fw_resources_init() to
check for the wifi-firmware subnode before attempting to parse the
memory regions.

Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Reviewed-by: Raj Kumar Bhagat <quic_rajkbhag@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20240904095815.1572186-2-caleb.connolly@linaro.org