arm64: Change cpu_resume() to enable mmu early then access sleep_sp by va

By enabling the MMU early in cpu_resume(), the sleep_save_sp and stack can
be accessed by VA, which avoids the need to convert-addresses and clean to
PoC on the suspend path.

MMU setup is shared with the boot path, meaning the swapper_pg_dir is
restored directly: ttbr1_el1 is no longer saved/restored.

struct sleep_save_sp is removed, replacing it with a single array of
pointers.

cpu_do_{suspend,resume} could be further reduced to not restore: cpacr_el1,
mdscr_el1, tcr_el1, vbar_el1 and sctlr_el1, all of which are set by
__cpu_setup(). However these values all contain res0 bits that may be used
to enable future features.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/kernel/setup.c

@@ -176,7 +176,6 @@ static void __init smp_build_mpidr_hash(void)
 	 */
 	if (mpidr_hash_size() > 4 * num_possible_cpus())
 		pr_warn("Large number of MPIDR hash buckets detected\n");
-	__flush_dcache_area(&mpidr_hash, sizeof(struct mpidr_hash));
 }
 
 static void __init setup_machine_fdt(phys_addr_t dt_phys)