aspeed: Move README.md to common base layer

Consolidate the 24xx/25xx layer READMEs into a single Aspeed BSP
README.

Change-Id: I7446f5241343d304d9f083c4baf2baa0ddff6234
Tested: Documentation only, no functional impact
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
@@ -0,0 +1,9 @@
+ASPEED
+================
+
+This is the ASPEED Board Support Package (BSP) layer.  It supports the
+AST2400 and AST2500; ARM service management SOCs made by ASPEED. More
+information about the AST2400 and AST2500 can be found
+[here](https://www.aspeedtech.com/products.php?fPath=20&rId=376)
+and
+[here](https://www.aspeedtech.com/products.php?fPath=20&rId=440).
diff --git a/meta-ast2400/README.md b/meta-ast2400/README.md
deleted file mode 100644
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--- a/meta-ast2400/README.md
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-ASPEED AST2400
-================
-
-This is the ASPEED AST2400 Board Support Package (BSP) layer.
-The AST2400 is an ARM, service management SOC made by ASPEED. More information
-about the AST2400 can be found
-[here](https://www.aspeedtech.com/products.php?fPath=20&rId=376).
-This layer should be included for all OpenBMC systems that use the AST2400.
diff --git a/meta-ast2500/README.md b/meta-ast2500/README.md
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index 2b4dc96..0000000
--- a/meta-ast2500/README.md
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-ASPEED AST2500
-================
-
-This is the ASPEED AST2500 Board Support Package (BSP) layer.
-The AST2500 is an ARM, service management SOC made by ASPEED. More information
-about the AST2500 can be found
-[here](https://www.aspeedtech.com/products.php?fPath=20&rId=440).
-This layer should be included for all OpenBMC systems that use the AST2500.