drm/vc4: fix krealloc() memory leak

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

drm/vc4: fix krealloc() memory leak

Don't just overwrite the original pointer passed to krealloc()

with its return value without checking latter:

MEM = krealloc(MEM, SZ, GFP);

If krealloc() returns NULL, that erases the pointer

to the still allocated memory, hence leaks this memory.

Instead, use a temporary variable, check it's not NULL

and only then assign it to the original pointer:

TMP = krealloc(MEM, SZ, GFP);

if (!TMP) return;

MEM = TMP;

While on it, use krealloc_array().