debug: Fix __bug_table[] in arch linker scripts

debug: Fix __bug_table[] in arch linker scripts

The kbuild test robot reported this build failure on a number
of architectures:

 >         make.cross ARCH=arm
 >    lib/lib.a(bug.o): In function `find_bug':
 > >> lib/bug.c:135: undefined reference to `__start___bug_table'
 > >> lib/bug.c:135: undefined reference to `__stop___bug_table'

Caused by:

  19d436268dde ("debug: Add _ONCE() logic to report_bug()")

Which moved the BUG_TABLE from RO_DATA_SECTION() to RW_DATA_SECTION(),
but a number of architectures don't use RW_DATA_SECTION(), so they
ended up with no __bug_table[] ...

Ideally all those would use RW_DATA_SECTION() in their linker scripts,
but that's for another day.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kbuild test robot <fengguang.wu@intel.com>
Cc: kbuild-all@01.org
Cc: tipbuild@zytor.com
Link: http://lkml.kernel.org/r/20170330154927.o6qmgfp4bdhrajbm@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>