clk: ls1028a: Fix warning on clamp() usage

These constants are used in clamp() with the value being clamped an
unsigned long. Make them unsigned long defines so that clamp() doesn't
complain about comparing different types.

In file included from include/linux/list.h:9,
                 from include/linux/kobject.h:19,
                 from include/linux/of.h:17,
                 from include/linux/clk-provider.h:9,
                 from drivers/clk/clk-plldig.c:8:
drivers/clk/clk-plldig.c: In function 'plldig_determine_rate':
include/linux/kernel.h:835:29: warning: comparison of distinct pointer types lacks a cast
  835 |   (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
      |

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Wen He <wen.he_1@nxp.com>
Fixes: d37010a3 ("clk: ls1028a: Add clock driver for Display output interface")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20200203052507.93215-1-sboyd@kernel.org