Kconfig: Migrate all of cmd/fastboot/Kconfig to defconfigs

- Move ANDROID_IMAGE_SUPPORT to top level Kconfig under images as it's
  not strictly part of fastboot.
- Add some defaults for the fastboot buffer location and size
- Migrate all options listed in cmd/fastboot/Kconfig
- Cleanup the README

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/fastboot/Kconfig b/cmd/fastboot/Kconfig
index b84529a..fb0c5da 100644
--- a/cmd/fastboot/Kconfig
+++ b/cmd/fastboot/Kconfig
@@ -2,6 +2,7 @@
 
 menuconfig FASTBOOT
 	bool "Fastboot support"
+	depends on USB_GADGET
 
 if FASTBOOT
 
@@ -20,16 +21,20 @@
 
 	  See doc/README.android-fastboot for more information.
 
-config ANDROID_BOOT_IMAGE
-	bool "Enable support for Android Boot Images"
-	help
-	  This enables support for booting images which use the Android
-	  image format header.
-
 if USB_FUNCTION_FASTBOOT
 
 config FASTBOOT_BUF_ADDR
 	hex "Define FASTBOOT buffer address"
+	default 0x82000000 if MX6SX || MX6SL || MX6UL || MX6SLL
+	default 0x81000000 if ARCH_OMAP2PLUS
+	default 0x42000000 if ARCH_SUNXI && !MACH_SUN9I
+	default 0x22000000 if ARCH_SUNXI && MACH_SUN9I
+	default 0x60800800 if ROCKCHIP_RK3036 || ROCKCHIP_RK3188 || \
+				ROCKCHIP_RK322X
+	default 0x800800 if ROCKCHIP_RK3288 || ROCKCHIP_RK3329 || \
+				ROCKCHIP_RK3399
+	default 0x280000 if ROCKCHIP_RK3368
+	default 0x100000 if ARCH_ZYNQMP
 	help
 	  The fastboot protocol requires a large memory buffer for
 	  downloads. Define this to the starting RAM address to use for
@@ -37,6 +42,10 @@
 
 config FASTBOOT_BUF_SIZE
 	hex "Define FASTBOOT buffer size"
+	default 0x8000000 if ARCH_ROCKCHIP
+	default 0x6000000 if ARCH_ZYNQMP
+	default 0x2000000 if ARCH_SUNXI
+	default 0x7000000
 	help
 	  The fastboot protocol requires a large memory buffer for
 	  downloads. This buffer should be as large as possible for a
@@ -59,7 +68,7 @@
 
 config FASTBOOT_FLASH_MMC_DEV
 	int "Define FASTBOOT MMC FLASH default device"
-	depends on FASTBOOT_FLASH
+	depends on FASTBOOT_FLASH && MMC
 	help
 	  The fastboot "flash" command requires additional information
 	  regarding the non-volatile storage device. Define this to