Fix printf format warning in iflib.c

[dim]

Summary

Clang 5.0.0 got better warnings about printf format strings using %zd,
and this leads to the following -Werror warning on arm:

sys/net/iflib.c:1517:8: error: format specifies type 'ssize_t' (aka 'int') but the argument has type 'bus_size_t' (aka 'unsigned long') [-Werror,-Wformat]
                                          sctx->isc_tx_maxsize, nsegments, sctx->isc_tx_maxsegsize);
                                          ^~~~~~~~~~~~~~~~~~~~
sys/net/iflib.c:1517:41: error: format specifies type 'ssize_t' (aka 'int') but the argument has type 'bus_size_t' (aka 'unsigned long') [-Werror,-Wformat]
                                          sctx->isc_tx_maxsize, nsegments, sctx->isc_tx_maxsegsize);
                                                                           ^~~~~~~~~~~~~~~~~~~~~~~

Fix this by casting bus_size_t arguments to uintmax_t, and using
%ju instead.

[emaste]

aside, there's come crazy whitespace going on in iflib.c

[emaste]

What about an (unsigned long) cast and %lu? Since bus_size_t is already unsigned long that seems to be reasonable, and doesn't require an unnecessary 64-bit value on ILP32 archs.

[dim]

In D11679#241912, @emaste wrote:

aside, there's come crazy whitespace going on in iflib.c

Yes, I thought to use the default 4 space continuation indent instead.

In D11679#241917, @emaste wrote:

What about an (unsigned long) cast and %lu? Since bus_size_t is already unsigned long that seems to be reasonable, and doesn't require an unnecessary 64-bit value on ILP32 archs.

As discussed on irc, not all arches use unsigned long, unfortunately:

sys/amd64/include/_bus.h: typedef uint64_t bus_size_t;
sys/arm/include/_bus.h: typedef u_long bus_size_t;
sys/arm64/include/_bus.h: typedef u_long bus_size_t;
sys/i386/include/_bus.h: typedef uint32_t bus_size_t;
sys/mips/include/_bus.h: typedef uintptr_t bus_size_t;
sys/powerpc/include/_bus.h: typedef vm_size_t bus_size_t;
sys/riscv/include/_bus.h: typedef u_long bus_size_t;
sys/sparc64/include/_bus.h: typedef u_long bus_size_t;