platform/x86: wmi: Do not mix pages and kmalloc

The probe handler_data was being allocated with __get_free_pages()
for no reason I could find. The error path was using kfree(). Since
other things are happily using kmalloc() in the probe path, switch to
kmalloc() entirely. This fixes the error path mismatch and will avoid
issues with CONFIG_HARDENED_USERCOPY_PAGESPAN=y.

Reported-by: Mihai Donțu <mihai.dontu@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Mario Limonciello <Mario.limonciello@dell.com>
Cc: stable@vger.kernel.org
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>