microblaze: Define empty mmiowb
microblaze: Define empty mmiowb

mmiowb is required by any driver.

Signed-off-by: Michal Simek <3a191dd2be46e826fee926d532b136ed65cb5318@monstr.eu>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs