KVM: MIPS: Drop @max param from mmu_topup_memory_cache()

Replace the @max param in mmu_topup_memory_cache() and instead use
ARRAY_SIZE() to terminate the loop to fill the cache.  This removes a
BUG_ON() and sets the stage for moving MIPS to the common memory cache
implementation.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200703023545.8771-20-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>