blackfin: don't use 'bool' when it causes problems

The use of 'bool' data types in globally used header files cases build
errors like this:

In file included from arch/blackfin/include/asm/blackfin.h:13:0,
                 from include/common.h:92,
                 from cmd_test.c:17:
arch/blackfin/include/asm/blackfin_local.h:54:1: error: unknown type name 'bool'

Use plain 'int' instead to avoid such kind of trouble.

Signed-off-by: Wolfgang Denk <wd@denx.de>