Use `grep -E` or plain `grep` instead of `egrep`

`egrep` has been deprecated in GNU grep since 2007,
and since 3.8 it emits obsolescence warnings:
https://git.savannah.gnu.org/cgit/grep.git/commit/?id=a9515624709865d480e3142fd959bccd1c9372d1
Acked-by: Dhruva Gole <d-gole@ti.com>
diff --git a/doc/board/intel/edison.rst b/doc/board/intel/edison.rst
index 5a65673..782d75a 100644
--- a/doc/board/intel/edison.rst
+++ b/doc/board/intel/edison.rst
@@ -90,7 +90,7 @@
 
 .. code-block:: none
 
-  lsusb | egrep "8087|8086"
+  lsusb | grep -E "8087|8086"
   Bus 001 Device 004: ID 8086:e005 Intel Corp.
 
 If you see a device with the same ID as above, the board is waiting for your