drm/exynos: fimd: fix clock leak on resume error path

exynos_fimd_resume() can fail when clk_prepare_enable() succeeds for
bus_clk but fails for lcd_clk. The function returns the error without
disabling bus_clk, leaving it prepared and enabled.

Disable bus_clk before returning the error to keep the clock state
balanced.

Signed-off-by: jiawen <1298662399@qq.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>