microblaze: switch to NO_BOOTMEM

microblaze: switch to NO_BOOTMEM

Microblaze doesn't set CONFIG_NO_BOOTMEM and so memblock_virt_alloc()
doesn't work for CONFIG_HAVE_MEMBLOCK && !CONFIG_NO_BOOTMEM.

Similar change was already done by others architectures
"ARM: mm: Remove bootmem code and switch to NO_BOOTMEM"
(sha1: 963411ec2cf51a5d23f63bedc92ebac3a6e7bb56)
or
"openrisc: Consolidate setup to use memblock instead of bootmem"
(sha1: a4730d5725db32f01b9abf18cfc6747c268e9267)
or
"parisc: Drop bootmem and switch to memblock"
(sha1: 753c8cb04aaf5bcfda5206a558043baa7114df1a)
or
"powerpc: Remove bootmem allocator"
(sha1: 2165cf6c99f163de69cd12c267ba85ad33245a5d)
or
"s390/mm: Convert bootmem to memblock"
(sha1: 379da7af451293030572a32121c1df9fa4ea52fb)
or
"sparc64: Convert over to NO_BOOTMEM."
(sha1: d8a8c86cad8ec9b0a769572a3119514d502b5d9e)
or
"xtensa: drop sysmem and switch to memblock"
(sha1: 5adfeab83a25d39502404eeb3acb4eac89ac064c)

Issue was introduced by:
"of/fdt: use memblock_virt_alloc for early alloc"
(sha1: 352afcebe37240723c93e0a0571d613a477712f0)

Signed-off-by: Rob Herring <robh@kernel.org>
Tested-by: Alvaro Gamez Machado <alvaro.gamez@hazent.com>
Tested-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>