sh: remove unused do_fpu_error

This does not appear to have been used since commit 74d99a5e ("sh:
SH-2A FPU support") in 2007.

Signed-off-by: Bobby Bingham <koorogi@koorogi.info>
Cc: Paul Mundt <paul.mundt@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>