habanalabs: Avoid using a non-initialized MMU cache mutex

The MMU cache mutex is used in the ASIC hw_init() functions, but it is
initialized only later in hl_mmu_init().
This patch prevents it by moving the initialization to the
device_early_init() function.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>