eatt: Make command queue available since channel is pending

This fixes following crash when channel is removed being in the PENDING
state

Revision: 'PROTO1.0'
ABI: 'arm64'
pid: 24104, tid: 24163, name: bt_main_thread  >>> com.google.android.bluetooth <<<
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x00000000000000a8
Cause: null pointer dereference
<snip>
(inlined)  std::__1::deque<tGATT_CMD_Q, std::__1::allocator<tGATT_CMD_Q>>::empty() const external/libcxx/include/deque:1330:50
0000000000xxxxxx  bluetooth::eatt::eatt_impl::remove_channel_by_cid(bluetooth::eatt::eatt_device*, unsigned short)
0000000000xxxxxx  bluetooth::eatt::eatt_impl::eatt_l2cap_error_cb(unsigned short, unsigned short)

Bug: 260709041
Tag: #feature
Test: compile
Change-Id: I21eac4f118456617122a26ec7764a811d4927279