Blackfin arch: unexport get_wchan

The only user of get_wchan I was able to find is the proc fs - and proc
can't be built modular.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

arch/blackfin/kernel/bfin_ksyms.c

@@ -65,7 +65,6 @@ EXPORT_SYMBOL(memset);
 EXPORT_SYMBOL(memcmp);
 EXPORT_SYMBOL(memmove);
 EXPORT_SYMBOL(memchr);
-EXPORT_SYMBOL(get_wchan);
 
 /*
  * libgcc functions - functions that are used internally by the