mfd: davinci_voicecodec: Fix possible null-ptr-deref davinci_vc_probe()

In the Linux kernel, the following vulnerability has been resolved:

mfd: davinci_voicecodec: Fix possible null-ptr-deref davinci_vc_probe()

It will cause null-ptr-deref when using 'res', if platform_get_resource()

returns NULL, so move using 'res' after devm_ioremap_resource() that

will check it to avoid null-ptr-deref.

And use devm_platform_get_and_ioremap_resource() to simplify code.