gatt: Improve send queued request from tGATT_TCB

This patch imidiatelly check if there is any outstanding, ready to send
message on the ATT CID 4 and if not, EATT channels are search for such
messages.

Withouth this patch code could end checking, if there is oustanding
request waiting for response.

Bug: 249431973
Test: atest BluetoothInstrumentationTests
Test: manual testes with device supporting EATT
Tag: #feature
Change-Id: I1d3351ebc82c4f1c0bf7bf0941c50c55bd4ec3e8