amd-xgbe: fix clang -Wformat warnings

When building with Clang we encounter the following warning:
| drivers/net/ethernet/amd/xgbe/xgbe-dcb.c:234:42: error: format specifies
| type 'unsigned char' but the argument has type '__u16' (aka 'unsigned
| short') [-Werror,-Wformat] pfc->pfc_cap, pfc->pfc_en, pfc->mbc,
| pfc->delay);

pfc->pfc_cap , pfc->pfc_cn, pfc->mbc are all of type `u8` while pfc->delay is
of type `u16`. The correct format specifiers `%hh[u|x]` were used for
the first three but not for pfc->delay, which is causing the warning
above.

Variadic functions (printf-like) undergo default argument promotion.
Documentation/core-api/printk-formats.rst specifically recommends using
the promoted-to-type's format flag. In this case `%d` (or `%x` to
maintain hex representation) should be used since both u8's and u16's
are fully representable by an int.

Moreover, C11 6.3.1.1 states:
(https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int
can represent all values of the original type ..., the value is
converted to an int; otherwise, it is converted to an unsigned int.
These are called the integer promotions.`

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20220708232653.556488-1-justinstitt@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>