Added comments : gic, virq, virqmap, Refactor : GIC feature, VIRQ map macro, guest context init

gic
 1. gic_test_configure_irq ->  gic_configure_irq
 2. gic_test_set_irq_handler -> gic_set_irq_handler
 3. remove unused parameter of gic_set_irq_handler, *pdata
VIRQ map macro
 1. Remove CFG_GUEST1_VIRQMAP because of It was used.
 2. CFG_GUEST0_VIRQMAP -> CFG_GUEST_VIRQMAP
guest context init
 1. There is duplicated code, so puts it for loop.