board: acer: picasso: add Acer Iconia Tab A500 support

The Acer Iconia A500 is a tablet computer designed, developed and
marketed by Acer Inc. It is powered by 1 GHz Nvidia Tegra 2 processor
and 1GB DDR2 RAM. The A500 is sold with 64 GB, although both 16 GB
and 32 GB models are available.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/doc/board/acer/index.rst b/doc/board/acer/index.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+ACER
+====
+
+.. toctree::
+   :maxdepth: 2
+
+   picasso