nimble/controller: Fix LE Connection Update status code in slave role
nimble/controller: Fix LE Connection Update status code in slave role

LE Connection Update called on slave when both sides do not support
Connection Parameters Request procedure should return "command
disallowed" error code. The "unknown HCI command" suggests that this
command is not supported at all which is not correct.

X-Original-Commit: ca655b536be7178557f7925622fe6bc29ce4808d

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble