virt: gunyah: rm_core: Clean up sequence idr earlier

When RM sends an error for a given call, Linux can re-use that sequence
number later. Presently, the sequence number is kept as reserved and
could cause a denial of service if many messages are crafted which
always return an RM error.

Change-Id: Icc2b054ab8d110c63759e30d62650ebc9d02b234
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>