BugLink: http://bugs.launchpad.net/bugs/1711401

Commit 2def86a7 ("hvc: Convert to using interrupts instead of opal
events") enabled the use of interrupts in the hvc_driver for OPAL
platforms. However on machines with more than one hvc console, any
console after the first will fail to register an interrupt handler in
notifier_add_irq() since all consoles share the same IRQ number but do
not set the IRQF_SHARED flag:

  genirq: Flags mismatch irq 31. 00000000 (hvc_console) vs. 00000000 (hvc_console)
  hvc_open: request_irq failed with rc -16.

This error propagates up to hvc_open() and the console is closed, but
OPAL will still generate interrupts that are not handled, leading to
rcu_sched stall warnings.

Set IRQF_SHARED when calling request_irq(), allowing additional consoles
to start properly. This is only set for consoles handled by
hvc_opal_probe(), leaving other types unaffected.
Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
(cherry picked from commit bbc3dfe8)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>