xsm: fix clang build

xsm: fix clang build

ebitmap.c:244:32: error: invalid conversion specifier 'Z' [-Werror,-Wformat-invalid-specifier]
               "match my size %Zd (high bit was %d)\n", mapunit,
                              ~^
ebitmap.c:245:16: error: format specifies type 'int' but the argument has type 'unsigned long'
      [-Werror,-Wformat]
               sizeof(u64) * 8, e->highbit);
               ^~~~~~~~~~~~~~~
ebitmap.c:245:33: error: data argument not used by format string [-Werror,-Wformat-extra-args]
               sizeof(u64) * 8, e->highbit);

Use %zd instead of %Zd, which is compliant with C99.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>