staging: rts_pstor: fix a bug that a greenhouse sd card can't be recognized

A greenhouse sd card can't be recognized using rts5209.
To fix this bug, these modifications are applied:
1, Move some codes which clear sd internal variables from sd_init_type to
sd_prepare_reset. So sd_init_type is useless any more and is removed
entirely;
2, If a sd card can't pass sd3.0 mode, the action of tunning phase should be
avoided when retrying sd2.0 mode.

Signed-off-by: wwang <wei_wang@realsil.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>