Allow L2CAP to send packets while changing link power state

L2CAP does not allow sending packets when link power state is changing.
Transitioning from sniff mode to active mode can take a long time. ACL
packets are allowed to be sent over sniff mode. Though they may take a
bit longer to transmit. Services may close the channel after enqueing
the packets assuming that L2CAP would transmit them. Any additional
delay in transmitting the L2CAP packets increases the probability that
the packets may get dropped locally.

Test: mmm packages/modules/Bluetooth
Flag: com.android.bluetooth.flags.transmit_smp_packets_before_release
Bug: 314417619
Bug: 357106628
Change-Id: I6f67e9659c70ecb71e7c8678d8f261513322e0f0