Audio HAL default implementation: reduce logspam

Legacy BT A2DP implementation of Audio HAL may be returning EAGAIN
from get_presentation_position, this is normal and shouldn't be
logged. Otherwise we create logspam as this HAL function is called
often.

Bug: 30222631
Change-Id: I9394dbc1d53c1f4136c2d538fccd519964ff1697
Test: play music via BT A2DP