iommu/ipmmu-vmsa: Don't truncate ttbr if LPAE is not enabled

If CONFIG_PHYS_ADDR_T_64BIT=n:

    drivers/iommu/ipmmu-vmsa.c: In function 'ipmmu_domain_init_context':
    drivers/iommu/ipmmu-vmsa.c:434:2: warning: right shift count >= width of type
      ipmmu_ctx_write(domain, IMTTUBR0, ttbr >> 32);
      ^

As io_pgtable_cfg.arm_lpae_s1_cfg.ttbr[] is an array of u64s, assigning
it to a phys_addr_t may truncates it.  Make ttbr u64 to fix this.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Joerg Roedel <jroedel@suse.de>