ANDROID: sched: rename sched_balance_find_src_group vendor hook

Change "android_rvh_find_busiest_group" to
"android_rvh_sched_balance_find_src_group"
that matches new naming convention.

Bug: 377200282

Change-Id: I0799491b8bdab0369f3a0f9e8c84a7f9929b6217
Signed-off-by: Peter-TY Tsai <peter-ty.tsai@mediatek.com>