boot/xilinx-prebuilt: merge hash files

There is actually no need to have two hash files for the xilinx-prebuilt
package.  As long as the boot/xilinx-prebuilt/xilinx-prebuilt.hash contains
the hash value for the default version as well as any version used by a
xilinx board defconfig, a single hash file is all that is needed.

In the future, when bumping the defconfig files independently of the
xilinx-prebuilt default version, all that has to be done is the following
process.

Patch Series:
1. Add new version hash to boot/xilinx-prebuilt/xilinx-prebuilt.hash.
2. Bump board defconfigs to new version.
3. Bump xilinx-prebuilt default version.

For this reason, this patch merges the two xilinx-prebuilt.hash files and
removes the board/xilinx xilinx-prebuilt.hash file.

Signed-off-by: Neal Frager <neal.frager@amd.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>

board/xilinx/patches/xilinx-prebuilt/xilinx-prebuilt.hash

@@ -1,2 +0,0 @@
-# Locally calculated
-sha256  ef61a4b249ecbf632a25cc34c3b03b8290be44397ff739467ac92ec1701e23bf  xilinx-prebuilt-xilinx_v2024.2.tar.gz