elf: Remove loading legacy hwcaps/platform entries in dynamic loader

The legacy hwcaps mechanism was removed with glibc 2.37:
See this commit series:
- d178c675
x86_64: Remove platform directory library loading test
- 6099908f
elf: Remove legacy hwcaps support from the dynamic loader
- b78ff5a2
elf: Remove legacy hwcaps support from ldconfig
- 4a709411
elf: Remove hwcap parameter from add_to_cache signature
- cfbf883d
elf: Remove hwcap and bits_hwcap fields from struct cache_entry
- 78d9a162
Add NEWS entry for legacy hwcaps removal
- ab40f203
elf: Remove _dl_string_hwcap
- e76369ed
elf: Simplify output of hwcap subdirectories in ld.so help

According to Florian Weimer, this was an oversight and should also
have been removed.

As ldconfig does not generate ld.so.cache entries with hwcap/platform
bits in the hwcap-field anymore, this patch now skips those entries.
Thus currently only named-hwcap-entries and the default entries are
allowed.
For named-hwcap entries bit 62 is set and also the isa-level bits can
be set.
For the default entries the hwcap-field is 0.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>