lib: utils: htif: Fix 32-bit build

When building 32-bit OpenSBI images, we get:

  lib/utils/sys/htif.c: In function '__check_fromhost':
  lib/utils/sys/htif.c:12:31: error: left shift count >= width of type
                                     [-Werror=shift-count-overflow]
   #define HTIF_DATA_MASK  ((1UL << HTIF_DATA_BITS) - 1)
                                 ^~

Fixes: c2f23cc6

 ("platform: Add Spike initial support")
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>