mx6: Remove duplication of iomuxc structure

There is no need to keep iomuxc_base_regs structure as it serves the exact same
purpose of the iomuxc structure, which is to provide access to the GPR
registers.

The additional fields of iomuxc_base_regs are not used. Other advantage of
'iomuxc' is that it has a shorter name and the variable declarations can fit
into a single line.

So remove iomuxc_base_regs structure and use iomuxc instead.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/board/boundary/nitrogen6x/nitrogen6x.c b/board/boundary/nitrogen6x/nitrogen6x.c
index 84294db..60a09f4 100644
--- a/board/boundary/nitrogen6x/nitrogen6x.c
+++ b/board/boundary/nitrogen6x/nitrogen6x.c
@@ -644,8 +644,7 @@
 
 int board_init(void)
 {
-	struct iomuxc_base_regs *const iomuxc_regs
-		= (struct iomuxc_base_regs *)IOMUXC_BASE_ADDR;
+	struct iomuxc *const iomuxc_regs = (struct iomuxc *)IOMUXC_BASE_ADDR;
 
 	clrsetbits_le32(&iomuxc_regs->gpr[1],
 			IOMUXC_GPR1_OTG_ID_MASK,