Fix memory leak for BTRC_ITEM_MEDIA.

Memory is allocated for each media item received from a remote phone for
AVRCP media browsing.  Although the media item itself was freed, the
memory for each attribute was not freed.  Move the allocation up to
the parent function such that it can be allocated and freed in the same
location.

Bug: 78222934
Test: dumpsys meminfo com.android.bluetooth
Change-Id: I217830441949642cd6ef0f96ac5fde9251452095