Update metadata doc for AIDL 2 bcradio HAL

Change "must be up to" to "should be <=" in Metadata of broadcast radio
HAL definition so that the format for metadata types is clear.

Bug: 318763229
Test: m -j
Change-Id: Ibd54988587170f2c20f7770be0f8376d9be2d3b2
1 file changed