x86: zboot: Create a separate ZBOOT option for zboot logic

Most of the functionality of zboot is contained in the logic which
handles a zimage. Create a separate Kconfig for the logic so that it can
(later) be used without the command itself being enabled.

Enable ZBOOT by default on x86, with the command depending on that. The
existing 'imply' can therefore be removed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

arch/Kconfig

@@ -246,7 +246,6 @@ config X86
 	imply CMD_PCI
 	imply CMD_SF
 	imply CMD_SF_TEST
-	imply CMD_ZBOOT
 	imply DM_GPIO
 	imply DM_KEYBOARD
 	imply DM_MMC

arch/x86/Kconfig

@@ -1053,4 +1053,12 @@ config SPL_COREBOOT_SYSINFO
 	  display, memory and build information. It is stored in
 	  struct sysinfo_t after parsing by get_coreboot_info().
 
+config ZBOOT
+	bool "Support the zImage format"
+	default y
+	help
+	  Enable this to support booting the x86-specific zImage format. This
+	  uses a special, binary format containing information about the Linux
+	  format to boot.
+
 endmenu

arch/x86/lib/Makefile

@@ -48,7 +48,7 @@ obj-$(CONFIG_$(SPL_TPL_)GENERATE_ACPI_TABLE) += acpi_table.o
 endif
 obj-y	+= tables.o
 ifndef CONFIG_SPL_BUILD
-obj-$(CONFIG_CMD_ZBOOT)	+= zimage.o
+obj-$(CONFIG_ZBOOT) += zimage.o
 endif
 obj-$(CONFIG_USE_HOB) += hob.o
 ifndef CONFIG_TPL_BUILD

cmd/Kconfig

@@ -538,6 +538,8 @@ config THOR_RESET_OFF
 
 config CMD_ZBOOT
 	bool "zboot - x86 boot command"
+	depends on ZBOOT
+	default y
 	help
 	  With x86 machines it is common to boot a bzImage file which
 	  contains both a kernel and a setup.bin file. The latter includes