ARM: imx: adapt clk_busy_mux to new clk_mux struct

Commit ce4f3313 (clk: add table lookup to mux) caused the following build
error on imx_v4_v5_defconfig/imx_v6_v7_defconfig:

arch/arm/mach-imx/clk-busy.c:172:11: error: 'struct clk_mux' has no member named 'width'

Fix it by passing the 'mask' field.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette@linaro.org: shortened $SUBJECT line]