ARM: Fix XIP kernels

Commit 7619751f ("ARM: 8595/2: apply more __ro_after_init") caused
a regression with XIP kernels by moving the __ro_after_init data into
the read-only section.  With XIP kernels, the read-only section is
located in read-only memory from the very beginning.

Work around this by moving the __ro_after_init data back into the .data
section, which will be in RAM, and hence will be writable.

It should be noted that in doing so, this remains writable after init.

Fixes: 7619751f ("ARM: 8595/2: apply more __ro_after_init")
Reported-by: NAndrea Merello <andrea.merello@gmail.com>
Tested-by: Andrea Merello <andrea.merello@gmail.com> [ XIP stm32 ]
Tested-by: NAlexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>

arch/arm/kernel/vmlinux-xip.lds.S

@@ -3,6 +3,9 @@
  * Written by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
  */
 
+/* No __ro_after_init data in the .rodata section - which will always be ro */
+#define RO_AFTER_INIT_DATA
+
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/cache.h>
 #include <asm/thread_info.h>
@@ -223,6 +226,8 @@ SECTIONS
 		. = ALIGN(PAGE_SIZE);
 		__init_end = .;
 
+		*(.data..ro_after_init)
+
 		NOSAVE_DATA
 		CACHELINE_ALIGNED_DATA(L1_CACHE_BYTES)
 		READ_MOSTLY_DATA(L1_CACHE_BYTES)