mmc: core: sd: implement proper support for sd3.0 au sizes

This reverts and updates commit 77776fd0 ("mmc: sd: fix the
maximum au_size for SD3.0"). The au_size for SD3.0 cannot be achieved
by a simple bit shift, so this needs to be implemented differently.
Also, don't print the warning in case of 0 since 'not defined' is
different from 'invalid'.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: stable <stable@vger.kernel.org> # [3.12, 3.13]
Signed-off-by: Chris Ball <chris@printf.net>