nios2: 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 8-bytes by adding '. = ALIGN(8);'
  to the final section before the symbol.
- Remove a now-spurious  '. = ALIGN(x);' statement that was intended to
  provide the above alignments.
- Ensure that we do have alignment by adding an ASSERT so that when not
  aligned we fail to link (and explain why).

Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

arch/nios2/cpu/u-boot.lds

@@ -60,8 +60,8 @@ SECTIONS
 	  *(.sdata)
 	  *(.sdata.*)
 	  *(.gnu.linkonce.s.*)
+	  . = ALIGN(8);
 	}
-	. = ALIGN(4);
 
 	_edata = .;
 	PROVIDE (edata = .);
@@ -124,3 +124,5 @@ SECTIONS
 	.debug_typenames 0 : { *(.debug_typenames) }
 	.debug_varnames	 0 : { *(.debug_varnames) }
 }
+
+ASSERT(_end % 8 == 0, "_end must be 8-byte aligned for device tree");