doc: board: Add Microchip MPFS Icicle Kit doc

This doc describes the procedure to build, flash and
boot Linux using U-boot on Microchip MPFS Icicle Kit.

Signed-off-by: Padmarao Begari <padmarao.begari@microchip.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
diff --git a/doc/board/index.rst b/doc/board/index.rst
index 915f1be..08c167b 100644
--- a/doc/board/index.rst
+++ b/doc/board/index.rst
@@ -17,6 +17,7 @@
    google/index
    intel/index
    kontron/index
+   microchip/index
    renesas/index
    rockchip/index
    sifive/index