iommu/io-pgtable: Move some initialization data to .init.rodata

The memory used by '__init' functions can be freed once the initialization
phase has been performed.

Mark some 'static const' array defined and used within some '__init'
functions as '__initconst', so that the corresponding data can also be
discarded.

Without '__initconst', the data are put in the .rodata section.
With the qualifier, they are put in the .init.rodata section.

With gcc 8.3.0, the following changes have been measured:

Without '__initconst':
   section      size
  .rodata       00000720
  .init.rodata  00000018

With '__initconst':
   section      size
  .rodata       00000660
  .init.rodata  00000058
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/io-pgtable-arm.c

@@ -1113,7 +1113,7 @@ static void __init arm_lpae_dump_ops(struct io_pgtable_ops *ops)
 
 static int __init arm_lpae_run_tests(struct io_pgtable_cfg *cfg)
 {
-	static const enum io_pgtable_fmt fmts[] = {
+	static const enum io_pgtable_fmt fmts[] __initconst = {
 		ARM_64_LPAE_S1,
 		ARM_64_LPAE_S2,
 	};
@@ -1212,13 +1212,13 @@ static int __init arm_lpae_run_tests(struct io_pgtable_cfg *cfg)
 
 static int __init arm_lpae_do_selftests(void)
 {
-	static const unsigned long pgsize[] = {
+	static const unsigned long pgsize[] __initconst = {
 		SZ_4K | SZ_2M | SZ_1G,
 		SZ_16K | SZ_32M,
 		SZ_64K | SZ_512M,
 	};
 
-	static const unsigned int ias[] = {
+	static const unsigned int ias[] __initconst = {
 		32, 36, 40, 42, 44, 48,
 	};