[lldb][AArch64] Don't check for VmFlags in smaps files

[lldb][AArch64] Don't check for VmFlags in smaps files

AArch64 kernel builds default to having /smaps and
the "VmFlags" line was added in 3.8. Long before MTE
was supported.

So we can assume that if you're AArch64 with MTE,
you can run this test.

The previous method of checking had a race condition
where the process we read smaps for, could finish before
we get to read the file.

I explored some alternatives but in the end I think
it's fine to just assume we have what we need.

Reviewed By: omjavaid

Differential Revision: https://reviews.llvm.org/D100493