Refactor the AUXV routines so they are more composable. In a future test
we want to look for many AUXV entries and we don't want to have to read
/proc/self/auxv each time.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
We want to use this in another test, so make it available at the top of
the powerpc selftests tree.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>