arm: MVE: Fix constant load pattern

arm: MVE: Fix constant load pattern

This patch fixes the constant load pattern for MVE, this was not accounting
correctly for label + offset cases.

Added test that ICE'd before and removed the scan assemblers for the mve_vector*
tests as they were too fragile.

gcc/ChangeLog:
2020-04-07  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* config/arm/arm.c (output_move_neon): Deal with label + offset cases.
	* config/arm/mve.md (*mve_mov<mode>): Handle const vectors.

gcc/testsuite/ChangeLog:
2020-04-07  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* gcc.target/arm/mve/intrinsics/mve_load_from_array.c: New test.
	* gcc.target/arm/mve/intrinsics/mve_vector_float.c: Remove
	scan-assembler.
	* gcc.target/arm/mve/intrinsics/mve_vector_float1.c: Likewise.
	* gcc.target/arm/mve/intrinsics/mve_vector_int1.c: Likewise.
	* gcc.target/arm/mve/intrinsics/mve_vector_int2.c: Likewise.