vexpress64: get rid of CONFIG_SYS_EXTRA_OPTIONS

The Versatile Express ARMv8 semihosted FVP platform is still
using the legacy CONFIG_SYS_EXTRA_OPTIONS method to configure
some compile-time flags. Get rid of this and create a Kconfig
entry for the FVP model, and a selectable bool for the
semihosting library.

The FVP subboard is now modeled as a target choice so we can
eventually choose between different ARMv8 versatile express
boards (FVP, base model, Juno...) this way. All dependent
symbols are updated to reflect this.

The 64bit Versatile Express board symbols are renamed
VEXPRESS64 so we have some chance to see what is actually
going on. Tested on the FVP fast model.

Acked-by: Steve Rae <srae@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 5eb1d03..d5399f1 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -51,6 +51,13 @@
         default "sa1100" if CPU_SA1100
 	default "armv8" if ARM64
 
+config SEMIHOSTING
+	bool "support boot from semihosting"
+	help
+	  In emulated environments, semihosting is a way for
+	  the hosted environment to call out to the emulator to
+	  retrieve files from the host machine.
+
 choice
 	prompt "Target select"
 
@@ -720,10 +727,15 @@
 	select CPU_ARM720T if SPL_BUILD
 	select CPU_V7 if !SPL_BUILD
 
-config TARGET_VEXPRESS_AEMV8A
+config TARGET_VEXPRESS64_AEMV8A
 	bool "Support vexpress_aemv8a"
 	select ARM64
 
+config TARGET_VEXPRESS64_BASE_FVP
+	bool "Support Versatile Express ARMv8a FVP BASE model"
+	select ARM64
+	select SEMIHOSTING
+
 config TARGET_LS2085A_EMU
 	bool "Support ls2085a_emu"
 	select ARM64