cnss2: Abstract of_reserved_mem_device_init() API

Currently in MSM platform reserved memory is attached to PCI
device of_node which may not apply to other non-MSM platforms.
Hence abstract the API using CONFIG_ARCH_QCOM flag.

Change-Id: Ic02b087c188b8dcb0959e17c80e72bb4021a725c
Signed-off-by: Yue Ma <yuem@codeaurora.org>