Remove remnants of optimization for > pagesize allocations.

[brooks]

Summary

In the past, this allocator seems to have allocated things larger than
a page seperately. Much of this code was removed at some point (perhaps
along with sbrk() used) so remove the rest. Instead, keep allocating in
power-of-two bins up to FIRST_BUCKET_SIZE << (NBUCKETS - 1). If we want
something more efficent, we should use a fancier allocator.

While here, remove some vestages of sbrk() use. Most importantly, don't
try to page align the pagepool since it's always page aligned by mmap().

[brooks]

I've now booted on amd64 in addition to CheriBSD.

[kib]

libexec/rtld-elf/rtld_malloc.c

135 ↗

(On Diff #61400)

isn't it make sense to include bucket < NBUCKETS into the condition where we return NULL ? I think it is better to use this condition instead of waiting for amt overflow.

180 ↗

(On Diff #61400)

This seems to be a dead check now ?

[brooks]

• Remove dead check.
• Return immediatly from the loop if bucket gets to big.