thermosphere: major refactor of memory map

- use recursive stage 1 page table (thanks @fincs for this idea)
- NULL now unmapped
- no identity mapping
- image + GICv2 now mapped at the same address for every platform
- tempbss mapped just after "real" bss, can now steal unused mem from
the latter
- no hardcoded VAs for other MMIO devices
- tegra: remove timers, use the generic timer instead

thermosphere/src/gicv2.h

@@ -143,11 +143,3 @@ typedef struct ArmGicV2VirtualInterfaceController {
     u8 _0xf4[0x100 - 0xF4];
     ArmGicV2ListRegister lr[64];
 } ArmGicV2VirtualInterfaceController;
-
-
-typedef struct ArmGicV2 {
-    volatile ArmGicV2Distributor *gicd;
-    volatile ArmGicV2Controller *gicc;
-    volatile ArmGicV2VirtualInterfaceController *gich;
-    volatile ArmGicV2Controller *gicv;
-} ArmGicV2;