lib/sort: adjust types

lib/sort: adjust types

First and foremost do away with the use of plain int for sizes or size-
derived values. Use size_t, despite this requiring some adjustment to
the logic. Also replace u32 by uint32_t.

While not directly related also drop a leftover #ifdef from x86's
swap_ex - this was needed only back when 32-bit Xen was still a thing.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>