mxs: ssp: Pull out the SSP bus to regs conversion

Create function which converts SSP bus number to SSP register pointer.
This functionality is reimplemented multiple times in the code, thus
make one common implementation. Moreover, make it a switch(), since the
SSP ports are not mapped in such nice linear fashion on MX23, therefore
having it a switch will simplify things there.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andy Fleming <afleming@freescale.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/cpu/arm926ejs/mxs/clock.c b/arch/arm/cpu/arm926ejs/mxs/clock.c
index 4ff19c3..5d6e12a 100644
--- a/arch/arm/cpu/arm926ejs/mxs/clock.c
+++ b/arch/arm/cpu/arm926ejs/mxs/clock.c
@@ -278,7 +278,7 @@
 	uint32_t reg;
 	uint32_t divide, rate, tgtclk;
 
-	ssp_regs = (struct mxs_ssp_regs *)(MXS_SSP0_BASE + (bus * 0x2000));
+	ssp_regs = mxs_ssp_regs_by_bus(bus);
 
 	/*
 	 * SSP bit rate = SSPCLK / (CLOCK_DIVIDE * (1 + CLOCK_RATE)),
diff --git a/arch/arm/include/asm/arch-mxs/regs-ssp.h b/arch/arm/include/asm/arch-mxs/regs-ssp.h
index cf52a28..4a75029 100644
--- a/arch/arm/include/asm/arch-mxs/regs-ssp.h
+++ b/arch/arm/include/asm/arch-mxs/regs-ssp.h
@@ -50,6 +50,22 @@
 	mxs_reg_32(hw_ssp_debug)
 	mxs_reg_32(hw_ssp_version)
 };
+
+static inline struct mxs_ssp_regs *mxs_ssp_regs_by_bus(unsigned int port)
+{
+	switch (port) {
+	case 0:
+		return (struct mxs_ssp_regs *)MXS_SSP0_BASE;
+	case 1:
+		return (struct mxs_ssp_regs *)MXS_SSP1_BASE;
+	case 2:
+		return (struct mxs_ssp_regs *)MXS_SSP2_BASE;
+	case 3:
+		return (struct mxs_ssp_regs *)MXS_SSP3_BASE;
+	default:
+		return NULL;
+	}
+}
 #endif
 
 #define	SSP_CTRL0_SFTRST			(1 << 31)