pinctrl: single: fix potential NULL dereference

mainline inclusion
from mainline-v6.2-rc5
commit d2d73e6d
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4L9
CVE: CVE-2022-48708

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d2d73e6d4822140445ad4a7b1c6091e0f5fe703b



--------------------------------

Added checking of pointer "function" in pcs_set_mux().
pinmux_generic_get_function() can return NULL and the pointer
"function" was dereferenced without checking against NULL.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 571aec4d ("pinctrl: single: Use generic pinmux helpers for managing functions")
Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20221118104332.943-1-korotkov.maxim.s@gmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>