fspacectl: remove unneeded freebsd32 wrapper

fspacectl(2) does not require special handling on freebsd32. The
presence of off_t in a struct does not cause it's size to change
between the native ABI and the 32-bit ABI supported by freebsd32
because off_t is always int64_t on BSD systems. Further, byte
order only requires handling for paired argument or return registers.

(32-byte alignment of 64-bit objects on i386 can require special
handling, but that situtation does not apply here.)

Reviewed by: kib, khng, emaste, delphij
Differential Revision: https://reviews.freebsd.org/D32994