dm_op: convert HVMOP_inject_trap and HVMOP_inject_msi

dm_op: convert HVMOP_inject_trap and HVMOP_inject_msi

NOTE: This patch also modifies the types of the 'vector', 'type' and
      'insn_len' arguments of xc_hvm_inject_trap() from uint32_t to
      uint8_t. In practice the values passed were always truncated to
      8 bits.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>