sh: includecheck fix: dwarf.c

fix the following 'make includecheck' warning:

  arch/sh/kernel/dwarf.c: asm/dwarf.h is included more than once.

Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>