Two simple uses of value_print_scalar_formatted

Two simple uses of value_print_scalar_formatted

A couple of spots could be easily converted to use
value_print_scalar_formatted.  This patch makes this change.

gdb/ChangeLog
2020-03-13  Tom Tromey  <tom@tromey.com>

	* printcmd.c (print_formatted): Use value_print_scalar_formatted.
	* mips-tdep.c (mips_print_register): Use
	value_print_scalar_formatted.