MIPS: defconfig: Cleanup from non-existing options

MIPS: defconfig: Cleanup from non-existing options

Remove options which do not exist anymore:
 - CPU_FREQ_DEBUG is gone since commit 2d06d8c49afd  ("[CPUFREQ] use
   dynamic debug instead of custom infrastructure").

 - ECONET is gone since commit 349f29d841db ("econet: remove ancient bug
   ridden protocol");

 - IPDDP_DECAP is gone since commit 9b5645b51384 ("appletalk: remove
   "config IPDDP_DECAP"");

Signed-off-by: Krzysztof Kozlowski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: [email protected]
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/16770/
Signed-off-by: Ralf Baechle <[email protected]>