mb/google/zork/Kconfig: remove unused option IRQ_SLOT_COUNT

That option is only relevant if the boards selects HAVE_PIRQ_TABLE which
it doesn't.

Change-Id: Ib5839a42f5133f5f84e1e1e4e587801b916ca571
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42787
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>

src/mainboard/google/zork/Kconfig

@@ -91,10 +91,6 @@ config MAX_CPUS
 	int
 	default 8
 
-config IRQ_SLOT_COUNT
-	int
-	default 11
-
 config ONBOARD_VGA_IS_PRIMARY
 	bool
 	default y