KVM: arm64: Populate ESR_ELx.EC for emulated SError injection

The hardware vSError injection mechanism populates ESR_ELx.EC as part of
ESR propagation and the contents of VSESR_EL2 populate the ISS field. Of
course, this means our emulated injection needs to set up the EC
correctly for an SError too.

Fixes: ce66109c ("KVM: arm64: nv: Take "masked" aborts to EL2 when HCRX_EL2.TMEA is set")
Link: https://lore.kernel.org/r/20250708230632.1954240-2-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>