[MIPS] TXx9: Miscellaneous build fixes

* Fix build if only RBTX4927 or RBTX4938 was selected.
* Move gpio helpers to generic part.
* Select SOC_TX4938 for RBTX4927/37 board.
* Fix parent of rbtx4938_fpga_resource.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/txx9/rbtx4938/setup.c b/arch/mips/txx9/rbtx4938/setup.c
index aaa987a..c2da923 100644
--- a/arch/mips/txx9/rbtx4938/setup.c
+++ b/arch/mips/txx9/rbtx4938/setup.c
@@ -457,7 +457,7 @@
 	rbtx4938_fpga_resource.start = CPHYSADDR(RBTX4938_FPGA_REG_ADDR);
 	rbtx4938_fpga_resource.end = CPHYSADDR(RBTX4938_FPGA_REG_ADDR) + 0xffff;
 	rbtx4938_fpga_resource.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
-	if (request_resource(&iomem_resource, &rbtx4938_fpga_resource))
+	if (request_resource(&txx9_ce_res[2], &rbtx4938_fpga_resource))
 		printk("request resource for fpga failed\n");
 
 	_machine_restart = rbtx4938_machine_restart;
@@ -488,18 +488,6 @@
 	return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 }
 
-/* GPIO support */
-
-int gpio_to_irq(unsigned gpio)
-{
-	return -EINVAL;
-}
-
-int irq_to_gpio(unsigned irq)
-{
-	return -EINVAL;
-}
-
 static DEFINE_SPINLOCK(rbtx4938_spi_gpio_lock);
 
 static void rbtx4938_spi_gpio_set(struct gpio_chip *chip, unsigned int offset,