ANDROID: gunyah: Sync with latest "gunyah: rsc_mgr: Add resource manager RPC core"

Align resource manager and rpc to v12 of Gunyah patches posted to
kernel.org.

 - Rename "buff" to "buf"
 - printk adjustments
 - Comments
 - Stylistic tweaks

https://lore.kernel.org/all/20230509204801.2824351-7-quic_eberman@quicinc.com/



Bug: 279506910
Change-Id: Iff216a9cb3afeb9de75f0b42bf58f139da2ca4bd
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>