gdbserver: Fix whitespace configure.srv damage for `i[34567]86-*-mingw*'

Fix fallout from commit 42cd72aa ("gdbserver: Make `make TAGS'
actually work") add a missing newline to configure.srv for
`i[34567]86-*-mingw*'.

	gdb/gdbserver/
	* configure.srv <i[34567]86-*-mingw*>: Fix whitespace damage.