elf: Remove extra hwcap mechanism from ldconfig

elf: Remove extra hwcap mechanism from ldconfig

Historically, this mechanism was used to process "nosegneg"
subdirectories, and it is still used to include the "tls"
subdirectories.  With nosegneg support gone from ld.so, this is part
no longer useful.

The entire mechanism is not well-designed because it causes the
meaning of hwcap bits in ld.so.cache to depend on the kernel version
that was used to generate the cache, which makes it difficult to use
this mechanism for anything else in the future.

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