hal: Set default backend sample rate for headset device

When music playback at 22.05Khz with headset, the afe
backend sample rate is set to 22.05khz as well. When
there is touch tone, it requires afe backend sample
rate to 48Khz. The rate change will cause music playback
disable and reroute to cause interruption during playback.

Fix it by setting backend sample rate to 48Khz if sample
rate less than 44.1Khz.

CRs-Fixed: 2258133
Change-Id: I711407537c0c41dbac99fea059710912ba6d1af3