serial: 8250_platform: simplify IRQF_SHARED handling

serial: 8250_platform: simplify IRQF_SHARED handling

IRQF_SHARED is the only flag handled in __serial8250_isa_init_ports()
and serial8250_probe_platform(). There is no need to precompute the
flags. Instead, initialize port->irqflags directly in the for loop.

Note the "if (bool)" is cheap and these are not hot paths anyway.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://patch.msgid.link/20251119092457.826789-7-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>