[ARM] Fix PR89222

The GCC optimizer can generate symbols with non-zero offset from simple
if-statements. Bit zero is used for the Arm/Thumb state bit, so relocations
with offsets fail if it changes bit zero and the relocation forces bit zero
to true.  The fix is to disable offsets on function pointer symbols.  

    gcc/
	PR target/89222
	* config/arm/arm.md (movsi): Use targetm.cannot_force_const_mem
	to decide when to split off a non-zero offset from a symbol.
	* config/arm/arm.c (arm_cannot_force_const_mem): Disallow offsets
	in function symbols.

    testsuite/
	PR target/89222
	* gcc.target/arm/pr89222.c: Add new test.

From-SVN: r269390