ipv6: fix clang Wformat warning

When building with 'make W=1', clang warns about a mismatched
format string:

net/ipv6/ah6.c:710:4: error: format specifies type 'unsigned short' but the argument has type 'int' [-Werror,-Wformat]
                        aalg_desc->uinfo.auth.icv_fullbits/8);
                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/printk.h:375:34: note: expanded from macro 'pr_info'
        printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
                                ~~~     ^~~~~~~~~~~
net/ipv6/esp6.c:1153:5: error: format specifies type 'unsigned short' but the argument has type 'int' [-Werror,-Wformat]
                                aalg_desc->uinfo.auth.icv_fullbits / 8);
                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/printk.h:375:34: note: expanded from macro 'pr_info'
        printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__)
                                ~~~     ^~~~~~~~~~~

Here, the result of dividing a 16-bit number by a 32-bit number
produces a 32-bit result, which is printed as a 16-bit integer.

Change the %hu format to the normal %u, which has the same effect
but avoids the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>