The driver limits the config space base to 32bit, however it can be
64bit on 64bit iMX hardware too. Remove that limitation. This patch
has no impact on the iMX6, which is the only SoC currently supported
by this driver.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>