[llvm-exegesis][X86] Use the same AGU counter estimate mapping for znver1 as znver2...

[llvm-exegesis][X86] Use the same AGU counter estimate mapping for znver1 as znver2, and count RMW ops as well

znver2 can use the ld/st dispatch counters to make a reasonable estimate for the AGU usage (although it misses complex LEA ops which I don't think we can fix), although it wasn't accounting for RMW ld-st uops which are counted separately - the same approach can be used for znver1 (ymm double-pumping ld/st agu is correctly measured as 2uops)

This change is mainly academic, but was noticed as the znver1/2 models incorrectly assume scalar RMW ops take 2uops