The conversion to generic kmap atomic broke microblaze by removing the
build fail.
Add it back.
Fixes: 7ac1b26b0a72 ("microblaze/mm/highmem: Switch to generic kmap atomic") Reported-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Michal Simek <monstr@monstr.eu>