pwm: spear: Fix checking return value of clk_enable() and clk_prepare()

commit 563861cd upstream.

The logic to check return value of clk_enable() and clk_prepare() is reversed,
fix it.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>