doc: Remove README.blackfin

U-Boot no longer supports blackfin architecture. Remove the doc.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

doc/README.blackfin

@@ -1,46 +0,0 @@
-Notes for the Blackfin architecture port of Das U-Boot
-
- =========
- ! ABOUT !
- =========
-
-<marketing blurb>
-Blackfin Processors embody a new breed of 16/32-bit embedded processor, ideally
-suited for products where a convergence of capabilities are necessary -
-multi-format audio, video, voice and image processing; multi-mode baseband and
-packet processing; control processing; and real-time security.  The Blackfin's
-unique combination of software flexibility and scalability has gained it
-widespread adoption in convergent applications.
-</marketing blurb>
-
-The Blackfin processor is wholly developed by Analog Devices Inc.
-
- ===========
- ! SUPPORT !
- ===========
-
-All open source code for the Blackfin processors are being handled via our
-collaborative website:
-http://blackfin.uclinux.org/
-
-In particular, bug reports, feature requests, help etc... for Das U-Boot are
-handled in the Das U-Boot sub project:
-http://blackfin.uclinux.org/gf/project/u-boot
-
-This website is backed both by an open source community as well as a dedicated
-team from Analog Devices Inc.
-
- =============
- ! TOOLCHAIN !
- =============
-
-To compile the Blackfin aspects, you'll need the GNU toolchain configured for
-the Blackfin processor.  You can obtain such a cross-compiler here:
-http://blackfin.uclinux.org/gf/project/toolchain
-
- =================
- ! DOCUMENTATION !
- =================
-
-For Blackfin specific documentation, you can visit our dedicated doc wiki:
-http://docs.blackfin.uclinux.org/doku.php?id=bootloaders:u-boot