ARM: Section based HYP idmap

Add a method (hyp_idmap_setup) to populate a hyp pgd with an
identity mapping of the code contained in the .hyp.idmap.text
section.

Offer a method to drop this identity mapping through
hyp_idmap_teardown.

Make all the above depend on CONFIG_ARM_VIRT_EXT and CONFIG_ARM_LPAE.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 11c1785..b571484 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -19,7 +19,11 @@
 	ALIGN_FUNCTION();						\
 	VMLINUX_SYMBOL(__idmap_text_start) = .;				\
 	*(.idmap.text)							\
-	VMLINUX_SYMBOL(__idmap_text_end) = .;
+	VMLINUX_SYMBOL(__idmap_text_end) = .;				\
+	ALIGN_FUNCTION();						\
+	VMLINUX_SYMBOL(__hyp_idmap_text_start) = .;			\
+	*(.hyp.idmap.text)						\
+	VMLINUX_SYMBOL(__hyp_idmap_text_end) = .;
 
 #ifdef CONFIG_HOTPLUG_CPU
 #define ARM_CPU_DISCARD(x)