nb/amd/pi/Kconfig: Drop unused Kconfig symbol

Change-Id: I713b3fed3fc6d55139badec93a67943dd93ced2a
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69333
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

src/northbridge/amd/pi/Kconfig

@@ -37,8 +37,4 @@ config HEAP_SIZE
 	hex
 	default 0xc0000
 
-config NUM_OF_IOAPICS
-	int
-	default 3
-
 endif # NORTHBRIDGE_AMD_PI