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>
diff --git a/configs/vct_platinum_onenand_small_defconfig b/configs/vct_platinum_onenand_small_defconfig
index f7b3a91..58c7995 100644
--- a/configs/vct_platinum_onenand_small_defconfig
+++ b/configs/vct_platinum_onenand_small_defconfig
@@ -1,3 +1,4 @@
 CONFIG_SYS_EXTRA_OPTIONS="VCT_PLATINUM,VCT_ONENAND,VCT_SMALL_IMAGE"
 CONFIG_MIPS=y
 CONFIG_TARGET_VCT=y
+# CONFIG_CMD_CRC32 is not set