[testsuite,arm] cmp-2.c: Move double-precision tests to cmp-3.c

[testsuite,arm] cmp-2.c: Move double-precision tests to cmp-3.c

Parts of the cmp-2.c test rely on double-precision support, making the
test fail on targets where the FPU supports single-precision only.

Split the test into single-precision (cmp-2.c) and double-precision
tests (cmp-3.c).

2020-03-24  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/testsuite/
	* gcc.target/arm/cmp-2.c: Move double-precision tests to...
	* gcc.target/arm/cmp-3.c: ...here (new file)