fpga: dfl-fme-region: Use platform_get_drvdata()

Use platform_get_drvdata() in remove() function of
the platform driver rather than dev_get_drvdata()
to match the platform_set_drvdata in the probe().

Signed-off-by: Moritz Fischer <mdf@kernel.org>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>