microblaze: Update linker scripts to ensure appended device tree is aligned

With commit 0535e46d55 ("scripts/dtc: Update to upstream version
v1.7.2-35-g52f07dcca47c") it is now a fatal error to U-Boot if our
device tree is not 8-byte aligned. In commit 85f586035d ("ARM: OMAP2+:
Pad SPL binary to 8-byte alignment before DTB") Beleswar Padhi explains
that we must have ALIGN(x) statements inside of a section to ensure that
padding is included and not simply that the linker address counter is
incremented. To that end, this patch:
- Aligns the final section before _end (for U-Boot) or _image_binary_end
  (for xPL phases) by 8-bytes by adjusting the ALIGN(4) statement to be
  ALIGN(8) in the final section before the symbol.
- Ensure that we do have alignment by adding an ASSERT so that when not
  aligned we fail to link (and explain why).

Tested-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

arch/microblaze/cpu/u-boot-spl.lds

@@ -50,7 +50,7 @@ SECTIONS
 		*(.bss)
 		*(.bss.*)
 		*(COMMON)
-		. = ALIGN(4);
+		. = ALIGN(8);
 		__bss_end = .;
 	}
 	_end = . ;
@@ -61,3 +61,6 @@ SECTIONS
 ASSERT(_end - _start <= (CONFIG_SPL_MAX_FOOTPRINT), \
         "SPL image plus BSS too big");
 #endif
+
+ASSERT(_image_binary_end % 8 == 0, \
+       "_image_binary_end must be 8-byte aligned for device tree");

arch/microblaze/cpu/u-boot.lds

@@ -67,8 +67,10 @@ SECTIONS
 		*(.scommon)
 		*(.bss*)
 		*(COMMON)
-		. = ALIGN(4);
+		. = ALIGN(8);
 		__bss_end = .;
 	}
 	_end = . ;
 }
+
+ASSERT(_end % 8 == 0, "_end must be 8-byte aligned for device tree");