powerpc/32: Drop unused grackle_set_stg()

The call to grackle_set_stg() ("Store Gathering") has always been inside
an #ifdef 0, since the code was first merged in v2.3.43pre7.

Apparently it was suspected of causing problems on some hardware so was
disabled. No one has ever proved otherwise so drop the code as unused
for now.
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Bjorn Helgaas <helgaas@kernel.org>
Closes: https://lore.kernel.org/all/20231031145600.GA9161@bhelgaas/Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231113051929.1952351-1-mpe@ellerman.id.au

arch/powerpc/sysdev/grackle.c

@@ -18,24 +18,8 @@
 #define GRACKLE_CFA(b, d, o)	(0x80 | ((b) << 8) | ((d) << 16) \
 				 | (((o) & ~3) << 24))
 
-#define GRACKLE_PICR1_STG		0x00000040
 #define GRACKLE_PICR1_LOOPSNOOP		0x00000010
 
-/* N.B. this is called before bridges is initialized, so we can't
-   use grackle_pcibios_{read,write}_config_dword. */
-static inline void grackle_set_stg(struct pci_controller* bp, int enable)
-{
-	unsigned int val;
-
-	out_be32(bp->cfg_addr, GRACKLE_CFA(0, 0, 0xa8));
-	val = in_le32(bp->cfg_data);
-	val = enable? (val | GRACKLE_PICR1_STG) :
-		(val & ~GRACKLE_PICR1_STG);
-	out_be32(bp->cfg_addr, GRACKLE_CFA(0, 0, 0xa8));
-	out_le32(bp->cfg_data, val);
-	(void)in_le32(bp->cfg_data);
-}
-
 static inline void grackle_set_loop_snoop(struct pci_controller *bp, int enable)
 {
 	unsigned int val;
@@ -56,7 +40,4 @@ void __init setup_grackle(struct pci_controller *hose)
 		pci_add_flags(PCI_REASSIGN_ALL_BUS);
 	if (of_machine_is_compatible("AAPL,PowerBook1998"))
 		grackle_set_loop_snoop(hose, 1);
-#if 0	/* Disabled for now, HW problems ??? */
-	grackle_set_stg(hose, 1);
-#endif
 }