kconfig: move CONFIG_CMD_CRC32 to Kconfig

Since CONFIG_CMD_CRC32 is defined in config_cmd_defaults.h,
it is enabled for all the boards except the ones undefining it
explicitly:
  kwb
  tseries_mmc
  tseries_nand
  tseries_spi
  vct_platinum_onenand_small
  vct_platinum_small
  vct_platinumavc_onenand_small
  vct_platinumavc_small
  vct_premium_onenand_small
  vct_premium_small

The default value of this config option should be "y" and
"# CONFIG_CMD_CRC32 is not set" should be added for those exceptions.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>