scripts/dtc: fix '%zx' warning

dtc uses an incorrect format specifier for printing a uint64_t value.
uint64_t may be either 'unsigned long' or 'unsigned long long' depending
on the host architecture.

Fix this by using %llx and casting to unsigned long long, which ensures
that we always have a wide enough variable to print 64 bits of hex.

    HOSTCC  scripts/dtc/checks.o
  scripts/dtc/checks.c: In function 'check_simple_bus_reg':
  scripts/dtc/checks.c:876:2: warning: format '%zx' expects argument of type 'size_t', but argument 4 has type 'uint64_t' [-Wformat=]
    snprintf(unit_addr, sizeof(unit_addr), "%zx", reg);
    ^
  scripts/dtc/checks.c:876:2: warning: format '%zx' expects argument of type 'size_t', but argument 4 has type 'uint64_t' [-Wformat=]

Link: http://lkml.kernel.org/r/20170829222034.GJ20805@n2100.armlinux.org.uk


Fixes: 828d4cdd012c ("dtc: check.c fix compile error")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>