image: Use the correct checks for CRC32

Add a host Kconfig for CRC32. With this we can use CONFIG_IS_ENABLED(CRC32)
directly in the host build, so drop the unnecessary indirection.

Add a few more conditions to SPL_CRC32 to avoid build failures as well as
TPL_CRC32. Also update hash.c to make crc32 optional and to actually take
notice of SPL_CRC32.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

lib/Makefile

@@ -96,9 +96,7 @@ obj-y += display_options.o
 CFLAGS_display_options.o := $(if $(BUILD_TAG),-DBUILD_TAG='"$(BUILD_TAG)"')
 obj-$(CONFIG_BCH) += bch.o
 obj-$(CONFIG_MMC_SPI) += crc7.o
-#ifndef CONFIG_TPL_BUILD
-obj-y += crc32.o
-#endif
+obj-$(CONFIG_$(SPL_TPL_)CRC32) += crc32.o
 obj-$(CONFIG_CRC32C) += crc32c.o
 obj-y += ctype.o
 obj-y += div64.o