mfd: sta2x11: Use GFP_KERNEL instead of GFP_ATOMIC

pci_driver probe functions aren't called with locks held and
thus don't need GFP_ATOMIC. Use GFP_KERNEL instead.

Problem found with Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220210204223.104181-10-Julia.Lawall@inria.fr