sb/amd/cimx/sb900: Change logical negation to bitwise

data &= !BIT0 will clear data, since !BIT0 evaluates to 0 (oops). We
only want to clear bit 0, not the whole thing, so use bitwise negation
instead.

Change-Id: I2179119e0d2d4aceaf4f8b499bf4c5baf4ef677f
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Found-by: Coverity CID 1241812
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33454
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/southbridge/amd/cimx/sb900/early.c

@@ -39,7 +39,7 @@ void sb_poweron_init(void)
 	//Enable/Disable PCI Bridge Device 14 Function 4.
 	outb(0xEA, 0xCD6);
 	data = inb(0xCD7);
-	data &= !BIT0;
+	data &= ~BIT0;
 	if (!CONFIG(PCIB_ENABLE)) {
 		data |= BIT0;
 	}