qemu-arm64: Enable POSITION_INDEPENDENT

Now that PIE works when U-Boot is started from ROM, let's enable
CONFIG_POSITION_INDEPENDENT, which allows to load U-Boot also via
ARM Trusted-Firmware's fip.bin to DRAM, without tweaking the
configuration.

To get a writable initial stack, we need to keep the fixed initial
stack pointer, which points to DRAM in our case.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0ecd0c6..a067a07 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -22,6 +22,7 @@
 
 config INIT_SP_RELATIVE
 	bool "Specify the early stack pointer relative to the .bss section"
+	default n if ARCH_QEMU
 	default y if POSITION_INDEPENDENT
 	help
 	  U-Boot typically uses a hard-coded value for the stack pointer