nimble/host: Fix host event buffer count
nimble/host: Fix host event buffer count

Fixes the problem of not putting events such as,
for example ble_hs_hci_evt_le_scan_timeout to the queue.

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