microblaze: Fix built-in DTB alignment to be 8-byte aligned

Commit 79edff1 ("scripts/dtc: Update to upstream version
v1.6.0-51-g183df9e9c2b9") broke booting on Microblaze systems depending on
the build. The problem is libfdt gained an 8-byte starting alignment check,
but the Microblaze built-in DTB area is only 4-byte aligned. This affected
not just built-in DTBs as bootloader passed DTBs are copied into the
built-in DTB region.

Other arches using built-in DTBs use a common linker macro which has
sufficient alignment.

Fixes: 79edff1 ("scripts/dtc: Update to upstream version v1.6.0-51-g183df9e9c2b9")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210213011624.251838-1-robh@kernel.org
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/kernel/vmlinux.lds.S

@@ -45,7 +45,7 @@ SECTIONS {
 		_etext = . ;
 	}
 
-	. = ALIGN (4) ;
+	. = ALIGN (8) ;
 	__fdt_blob : AT(ADDR(__fdt_blob) - LOAD_OFFSET) {
 		_fdt_start = . ;		/* place for fdt blob */
 		*(__fdt_blob) ;			/* Any link-placed DTB */