xen/arm: Kconfig: ACPI should depend on UEFI

On Arm, it is not possible to use ACPI without UEFI. In fact disabling
UEFI but not ACPI will lead to a compilation error:

ld: prelink.o: in function `acpi_os_get_root_pointer':
/builds/xen-project/people/andyhhp/xen/xen/drivers/acpi/osl.c:73:
undefined reference to `efi'
/builds/xen-project/people/andyhhp/xen/xen/drivers/acpi/osl.c:73:(.init.text+0x8ac0):
relocation truncated to fit: R_AARCH64_ADR_PREL_PG_HI21 against
undefined symbol `efi'

So make the dependency clear in the Kconfig.

This was spotted by the randconfig build in gitlab CI.

Fixes: 12314be574 ("xen/arm: make ARM_EFI selectable for Arm64")
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

xen/arch/arm/Kconfig

@@ -63,11 +63,11 @@ source "arch/Kconfig"
 
 config ACPI
 	bool "ACPI (Advanced Configuration and Power Interface) Support (UNSUPPORTED)" if UNSUPPORTED
-	depends on ARM_64
+	depends on ARM_64 && ARM_EFI
 	---help---
 
 	  Advanced Configuration and Power Interface (ACPI) support for Xen is
-	  an alternative to device tree on ARM64.
+	  an alternative to device tree on ARM64. This requires UEFI.
 
 config ARM_EFI
 	bool "UEFI boot service support"