Don't count total number of instructions for checking small functions

We don't want to instrument small functions. We need to just check if a
function has more than the specified number of instructions. We don't
need to count total number of instructions. We can return early once we
are above the threshold.

Bug: 352518093
Test: art/test.py
Flag: com.android.art.rw.flags.enable_profile_code_rw
Change-Id: Ib794fb977aeb0d09e97e8d33ba7e763f00aa1430