dsp5680xx: disable for now, it generates warnings

Use "git revert <commit>" to revert this commit, then build and
repair and post patch to the mailing list.

Warnings generated with:

nios2-elf-gcc (GCC) 3.4.6 (Altera Nios II 9.1 b222)

openocd/src/target/dsp5680xx.c: In function 'eonce_rx_upper_data':
openocd/src/target/dsp5680xx.c:252: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c: In function 'eonce_rx_lower_data':
openocd/src/target/dsp5680xx.c:268: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c: In function 'eonce_pc_store':
openocd/src/target/dsp5680xx.c:508: warning: dereferencing type-punned
pointer will break strict-aliasing rules
openocd/src/target/dsp5680xx.c: In function 'dsp5680xx_read':
openocd/src/target/dsp5680xx.c:736: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c:737: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c: In function 'dsp5680xx_write_8':
openocd/src/target/dsp5680xx.c:823: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c: In function 'dsp5680xx_write':
openocd/src/target/dsp5680xx.c:938: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c:941: warning: cast increases required
alignment of target type
openocd/src/target/dsp5680xx.c: In function 'dsp5680xx_f_wr':
openocd/src/target/dsp5680xx.c:1355: warning: cast increases required
alignment of target type