docs: add mt6795 to deprecated list

Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Change-Id: I2b3aa9bd0c23c360ecee673c68e1b2c92bc6d2be

docs/plat/deprecated.rst

@@ -16,3 +16,5 @@ List of deprecated platforms
 +================+================+====================+====================+
 |    sgm775      |      Arm       |        2.5         |       2.7          |
 +----------------+----------------+--------------------+--------------------+
+|    mt6795      |      MTK       |        2.5         |       2.7          |
++----------------+----------------+--------------------+--------------------+