Fix %llx/%lx build warnings on powerpc

Fix %llx/%lx build warnings on powerpc

powerpc64 uses the int-l64 type definitions, so we get an unsigned long
for our __u64 type. This causes several build warnings when we're
printing with %llx in tests/register.c and example/discover-loop.c, as
it's an unsigned long, not an unsigned long long.

One way to fix this would be to use the PRIx64 definitions from
inttypes.h - however, those are keyed off the __WORDSIZE definition,
essentially:

    # if __WORDSIZE == 64
    #  define PRIx64	"lx"
    # else
    #  define PRIx64	"llx"
    # endif

- and that breaks on x86_64, where our __u64 is an unsigned long long,
and would need %llx.

The powerpc types header does give us an option to use the int-l64
definitions though:

    /*
     * This is here because we used to use l64 for 64bit powerpc
     * and we don't want to impact user mode with our change to ll64
     * in the kernel.
     *
     * However, some user programs are fine with this.  They can
     * flag __SANE_USERSPACE_TYPES__ to get int-ll64.h here.
     */
    #if !defined(__SANE_USERSPACE_TYPES__) && defined(__powerpc64__) && !defined(__KERNEL__)
    # include <asm-generic/int-l64.h>
    #else
    # include <asm-generic/int-ll64.h>
    #endif

... and in our case we are in fact fine with this. So, #define
__SANE_USERSPACE_TYPES__ for the two example programs.

We refrain from doing this to the library headers though, as we have no
idea what libnvme users will need for __u64.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>