Fix the calculation of bta_sys_get_remaining_ticks

Previously, bta_sys_get_remaining_ticks() calculated the remaining
ticks for all the items in the hash map, which is incorrect.
Instead, we need to calculate the remaining ticks only for the queried
item.

Bug: 26110234

Change-Id: Ia867c1d0da15809a643b946f7d8b9143e3882935