soc: kunpeng_hccs: fix size_t format string

Printing a size_t using the %lu format string causes a warning on
architectures that define the type as 'unsigned int':

In file included from include/linux/device.h:15,
                 from include/linux/acpi.h:14,
                 from drivers/soc/hisilicon/kunpeng_hccs.c:25:
drivers/soc/hisilicon/kunpeng_hccs.c: In function 'hccs_get_bd_info':
drivers/soc/hisilicon/kunpeng_hccs.c:441:25: error: format '%lu' expects argument of type 'long unsigned int', but argument 3 has type 'size_t' {aka 'unsigned int'} [-Werror=format=]

Use the correct %zu format instead.

Fixes: 886bdf9c ("soc: hisilicon: Support HCCS driver on Kunpeng SoC")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>