base: Handle zero fill in cprintf when printing floats.

The fill_zero flag was being followed for ints, but not for floats.
This makes the cprintf unit test pass.

Change-Id: I4d17a3c9327aea05e0a3c81be1886c0c9256f03c
Reviewed-on: https://gem5-review.googlesource.com/6322
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

src/base/cprintf_formats.hh

@@ -151,6 +151,9 @@ _format_float(std::ostream &out, const T &data, Format &fmt)
 
     ios::fmtflags flags(out.flags());
 
+    if (fmt.fill_zero)
+        out.fill('0');
+
     switch (fmt.float_format) {
       case Format::scientific:
         if (fmt.precision != -1) {