lib: sbi: add some macros to detect BUG at runtime

Three macros are added. One is called BUG, which is used to put in an
unreachable branch. One is called BUG_ON, which is used to check bugs
and assert conditions are opposite. One is called SBI_ASSERT, used for
assertion checking.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>