soc/intel/common/block: Move gspi common functions into block/gspi

This patch cleans soc/intel/{apollolake/cannonlake/skylake} by moving
common soc code into common/block/gspi.

BUG=b:78109109
BRANCH=none
TEST=Build and boot KBL/CNL/APL platform.

Change-Id: I877c7c48af928ca1e0399ec794d9400bc52edfcb
Signed-off-by: Ravi Sarawadi <ravishankar.sarawadi@intel.com>
Signed-off-by: Maulik V Vaghela <maulik.v.vaghela@intel.com>
Signed-off-by: Subrata Banik <subrata.banik@intel.com>
Reviewed-on: https://review.coreboot.org/26048
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/soc/intel/cannonlake/spi.c

@@ -32,18 +32,3 @@ int spi_soc_devfn_to_bus(unsigned int devfn)
 	}
 	return -1;
 }
-
-int spi_soc_bus_to_devfn(unsigned int bus)
-{
-	switch (bus) {
-	case 0:
-		return PCH_DEVFN_SPI;
-	case 1:
-		return PCH_DEVFN_GSPI0;
-	case 2:
-		return PCH_DEVFN_GSPI1;
-	case 3:
-		return PCH_DEVFN_GSPI2;
-	}
-	return -1;
-}