BLE operation timeouts increased

[philips77]

This PR increases the timeouts for all BLE operations:

1. Short timeout, for quick operations was increased from 1 sec to 2.5 seconds.
2. Medium timeout changed from 2.5 sec to 5 seconds.
3. Long timeout, mainly used by "erase" operations was increased from 30 to 40 seconds. This change has less to do with BLE performance, but to prevent timeouts when erasing memory of larger devices.

The reason for the change is to support older devices after a packet size has been increased recently. Devices running NCS 2+ can send 2475 bytes per single SMP packet, which on older Android phones takes long time.

This PR fixes #72. Hopefully. Tested on Samsung Folder with Android 6.0.1 and it was enough to make both DFU and FS operations successful.