misc: rtsx: Add support for RTS5261

Add support for new chip rts5261.
In order to support rts5261, the definitions of some internal registers
and workflow have to be modified and are different from its predecessors.
So we need this patch to ensure RTS5261 can work.

Signed-off-by: Rui Feng <rui_feng@realsil.com.cn>
Link: https://lore.kernel.org/r/1571645105-5028-1-git-send-email-rui_feng@realsil.com.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>