elf: Do not read hwcaps from the vDSO in ld.so

elf: Do not read hwcaps from the vDSO in ld.so

This was only ever used for the "nosegneg" flag.  This approach for
passing hardware capability information creates a subtle dependency
between the kernel and userspace, and ld.so.cache contents.  It seems
inappropriate for toady, where people expect to be able to run
system images which very different kernel versions.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>