imgtec/pistachio: Fix memlayout ASSERT with new binutils

With binutils 2.26 our memlayout ASSERT for mirrored SRAM regions
gets confused due to the lack of parentheses grouping the expressions.

This fixes the following issue:

    LINK       cbfs/fallback/bootblock.debug
    mipsel-elf-ld.bfd: bootblock and gram_bootblock do not match!
    mipsel-elf-ld.bfd: romstage and kseg0_romstage do not match!

Change-Id: Ib406e229b8a552d9ffc4538b55ee0269bfed62a8
Signed-off-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-on: https://review.coreboot.org/14440
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/soc/imgtec/pistachio/include/soc/memlayout.ld

@@ -20,8 +20,8 @@
 /* SRAM memory is mapped in two different locations. Define regions in both for
  * full overlap checking and use this to guarantee they're kept in sync. */
 #define ASSERT_MIRRORED(r1, r2) \
-	_ = ASSERT(_e##r1 - _##r1 == _e##r2 - _##r2 && \
-		   _##r1 & 0x7fffffff == _##r2 & 0x7fffffff, \
+	_ = ASSERT((_e##r1 - _##r1) == (_e##r2 - _##r2) && \
+		   (_##r1 & 0x7fffffff) == (_##r2 & 0x7fffffff), \
 		   STR(r1 and r2 do not match!));
 
 SECTIONS