Make the literal argument to pow a double, not an integer

Make the literal argument to pow a double, not an integer

Since pow takes doubles, pass 2.0 instead of 2 to pow ().

Conveniently, this fixes the ambiguous call to pow on Solaris 11
with gcc 5.5 (gcc211 on the compile farm), which has a "using std::pow"
directive in a system header, which brings in float/double/long double
overloads.  Fixes the build on Solaris with enable-targets=all.

gdb/ChangeLog:

2019-12-19  Christian Biesinger  <cbiesinger@google.com>

	* score-tdep.c (score7_analyze_prologue): Pass 2.0 instead of
	2 to pow ().

Change-Id: Ib18e7e4749ddcbff0727b72a31198f8cb84d1993