ramips: use default lzma dictionary size for better performance

limit dictionary size patch was introduced to solve the well known
"LZMA ERROR 1 - must RESET board to recover" error.
09b6755946409d8fd8 "ramips: limit dictionary size for lzma compression"

It seems that it has failed recently and we can use lzma loader to fix
this error by adding "$(Device/uimage-lzma-loader)". So just remove it
to use the default parameter -d24 for a higher compression ratio.

Signed-off-by: Shiji Yang <yangshiji66@qq.com>