microblaze: Cleanup unused functions

These functions haven't been used, so just remove them. The patch
just uses grep to verify.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Michal Simek <monstr@monstr.eu>
Link: https://lore.kernel.org/r/1622350408-44875-3-git-send-email-guoren@kernel.org


Signed-off-by: Michal Simek <michal.simek@xilinx.com>