[MTK] [CONVERGENCE] [ALPS07745105] Fix SWT when switch codec

[Detail] When switch codec, BT hal will calculate the
elapsed time since last out_write to sleep. If don't
set default value to last_write_time_us_, it may get
a wrong time to sleep for a long time in out_write.
It will cause Auidofinger work wrong.

[Solution] Set default value to last_write_time_us_

Bug: 328847539
Fix: 328847539
Test: m com.android.btservices
Flag: EXEMPT, minor bug fix
Change-Id: I323586ab5fc207980f8c36b336d2ebc5b4c65b00