[Bug target/59952] -march=core-avx2 should not enable RTM

[thiago at kde dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59952

--- Comment #19 from Thiago Macieira <thiago at kde dot org> ---
The prefix can be emitted for any CPU, you don't need a flag for that. However,
you cannot emit the XTEST instruction unless the CPU has HLE or RTM.