simpleperf: change based on jit debug interface change.

1. Change magic field and sizeof_entry check for JITDescriptor.
2. Use seqlock field in JITCodeEntryV2 to check its valid.
3. Allow but skip entry with symfile_size = 0 in V2.

Bug: 141558390
Test: run simpleperf_unit_test.
Change-Id: I30e214597cec78c73492fdfeac1f9766b775f0e3
2 files changed