MIPS assembly pack: default heuristic detection to little-endian.

Current endianness detection is somewhat opportunistic and can fail
in cross-compile scenario. Since we are more likely to cross-compile
for little-endian now, adjust the default accordingly.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5613)

crypto/aes/asm/aes-mips.pl

@@ -88,7 +88,7 @@ $pf = ($flavour =~ /nubi/i) ? $t0 : $t2;
 #
 ######################################################################
 
-$big_endian=(`echo MIPSEL | $ENV{CC} -E -`=~/MIPSEL/)?1:0 if ($ENV{CC});
+$big_endian=(`echo MIPSEB | $ENV{CC} -E -`=~/MIPSEB/)?0:1 if ($ENV{CC});
 
 for (@ARGV) {	$output=$_ if (/\w[\w\-]*\.\w+$/);	}
 open STDOUT,">$output";

crypto/sha/asm/sha1-mips.pl

@@ -75,7 +75,7 @@ if ($flavour =~ /64|n32/i) {
 #
 ######################################################################
 
-$big_endian=(`echo MIPSEL | $ENV{CC} -E -`=~/MIPSEL/)?1:0 if ($ENV{CC});
+$big_endian=(`echo MIPSEB | $ENV{CC} -E -`=~/MIPSEB/)?0:1 if ($ENV{CC});
 
 for (@ARGV) {	$output=$_ if (/\w[\w\-]*\.\w+$/);   }
 open STDOUT,">$output";

crypto/sha/asm/sha512-mips.pl

@@ -81,7 +81,7 @@ $pf = ($flavour =~ /nubi/i) ? $t0 : $t2;
 #
 ######################################################################
 
-$big_endian=(`echo MIPSEL | $ENV{CC} -E -`=~/MIPSEL/)?1:0 if ($ENV{CC});
+$big_endian=(`echo MIPSEB | $ENV{CC} -E -`=~/MIPSEB/)?0:1 if ($ENV{CC});
 
 for (@ARGV) {	$output=$_ if (/\w[\w\-]*\.\w+$/);	}
 open STDOUT,">$output";