Unlike (synchronous) exception handlers, interrupt handlers don't normally
have a need to know the outer context's register state. Similarly, the vast
majority of key handlers has no need for such.

1: IRQ: generalize [gs]et_irq_regs()
2: serial: fake IRQ-regs context in poll handlers
3: keyhandler: drop regs parameter from handle_keyregs()
4: serial: drop serial_rx_fn's regs parameter
5: PV-shim: drop pv_console_rx()'s regs parameter
6: serial: drop serial_[rt]x_interrupt()'s regs parameter
7: IRQ: drop regs parameter from handler functions
8: x86/APIC: drop regs parameter from direct vector handler functions

Jan