sh: sh7753evb: Fix build error

sh: sh7753evb: Fix build error

Currently buildman fails to build sh7753evb and reports the following:

  board/renesas/sh7753evb/built-in.o: In function 'init_gether_mdio':
  board/renesas/sh7753evb/sh7753evb.c:94: undefined reference to 'PMB_ADDR_BASE'
  board/renesas/sh7753evb/sh7753evb.c:94: undefined reference to 'PMB_DATA_BASE'
  board/renesas/sh7753evb/sh7753evb.c:94: undefined reference to 'mk_pmb_addr_val'
  board/renesas/sh7753evb/sh7753evb.c:94: undefined reference to 'mk_pmb_data_val'
  make: *** [u-boot] Error 1

The fix is to wrap any codes that access these macros with CONFIG_SH_32BIT.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>