lra: Reallow reloading user hard registers if the insn is not asm [PR 120983]

The PR 87600 fix has disallowed reloading user hard registers to resolve
earlyclobber-induced conflict.

However before reload, recog completely ignores the constraints of
insns, so the RTL passes may produce insns where some user hard
registers violate an earlyclobber.  Then we'll get an ICE without
reloading them, like what we are recently encountering in LoongArch test
suite.

IIUC "recog does not look at constraints until reload" has been a
well-established rule in GCC for years and I don't have enough skill to
challange it.  So reallow reloading user hard registers (but still
disallow doing so for asm) to fix the ICE.

gcc/ChangeLog:

	PR rtl-optimization/120983
	* lra-constraints.cc (process_alt_operands): Allow reloading
	user hard registers unless the insn is an asm.

(cherry picked from commit e6d3c88e7bb07f94308074f9751e4384a191e022)