readelf: use PRIu16 instead of PRId16 for uint16_t

The Elfxx_Half type is unsigned, thus it should be printed as an unsigned
type.  This fixes the formatting of such a value if it is bigger than
32767, which would be printed as a negative number with the PRId16 format,
due to a recent change in glibc that properly converts the value to the
narrow type before printing.

Fixes this testsuite failure:

@@ -14,7 +14,7 @@
   Flags:
   Size of this header:               64 (bytes)
   Size of program header entries:    56 (bytes)
-  Number of program headers entries: -1 (66000 in [0].sh_info)
+  Number of program headers entries: 65535 (66000 in [0].sh_info)
   Size of section header entries:    64 (bytes)
   Number of section headers entries: 1
   Section header string table index: 0
FAIL run-getphdrnum.sh (exit status: 1)

0 files changed, 0 insertions, 0 deletions