clk: mvebu: armada-37xx-periph: Use PTR_ERR_OR_ZERO()

Fix ptr_ret.cocci warnings:
drivers/clk/mvebu/armada-37xx-periph.c:362:1-3: WARNING: PTR_ERR_OR_ZERO can be used

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Signed-off-by: Vasyl Gomonovych <gomonovych@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>