selftests: gpio: Use "grep -E" instead of "egrep"

The latest version of grep claims the egrep is now obsolete so the build
now contains warnings that look like:
	egrep: warning: egrep is obsolescent; using grep -E
fix this up by moving the related file to use "grep -E" instead.

  sed -i "s/egrep/grep -E/g" `grep egrep -rwl tools/testing/selftests/gpio`

Here are the steps to install the latest grep:

  wget http://ftp.gnu.org/gnu/grep/grep-3.8.tar.gz
  tar xf grep-3.8.tar.gz
  cd grep-3.8 && ./configure && make
  sudo make install
  export PATH=/usr/local/bin:$PATH
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/gpio/gpio-sim.sh

@@ -27,7 +27,7 @@ remove_chip() {
 			continue
 		fi
 
-		LINES=`ls $CONFIGFS_DIR/$CHIP/$BANK/ | egrep ^line`
+		LINES=`ls $CONFIGFS_DIR/$CHIP/$BANK/ | grep -E ^line`
 		if [ "$?" = 0 ]; then
 			for LINE in $LINES; do
 				if [ -e $CONFIGFS_DIR/$CHIP/$BANK/$LINE/hog ]; then