Move the IRQ fix from generic to ar71xx specific.
Other targets like ath79 have specific pathes to delete this code.
This resulted in a build failure on ath79
While at it, wipe the 4.19 version, as ar71xx will never reach this.
Fixes: 530f76708cef ("ar71xx: Fix potentially missed IRQ handling during
dispatch")
Signed-off-by: Koen Vandeputte <koen.vandeputte@ncentric.com>
