mmc/dwmmc: modify FIFO threshold only if value explicitly set

If platform provides "host->fifoth_val" it will be used for
initialization of DWMCI_FIFOTH register. Otherwise default value will be
used.

This implementation allows:
 * escape unclear and recursive calculations that are currently in use
 * use whatever custom value for DWMCI_FIFOTH initialization if any
particular SoC requires it

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

Cc: Mischa Jonker <mjonker@synopsys.com>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Amar <amarendra.xt@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
Cc: Andy Fleming <afleming@freescale.com>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Pantelis Antoniou <panto@antoniou-consulting.com>

drivers/mmc/dw_mmc.c

@@ -299,7 +299,6 @@ static void dwmci_set_ios(struct mmc *mmc)
 static int dwmci_init(struct mmc *mmc)
 {
 	struct dwmci_host *host = (struct dwmci_host *)mmc->priv;
-	u32 fifo_size;
 
 	if (host->board_init)
 		host->board_init(host);
@@ -322,13 +321,9 @@ static int dwmci_init(struct mmc *mmc)
 	dwmci_writel(host, DWMCI_IDINTEN, 0);
 	dwmci_writel(host, DWMCI_BMOD, 1);
 
-	if (!host->fifoth_val) {
-		fifo_size = dwmci_readl(host, DWMCI_FIFOTH);
-		fifo_size = ((fifo_size & RX_WMARK_MASK) >> RX_WMARK_SHIFT) + 1;
-		host->fifoth_val = MSIZE(0x2) | RX_WMARK(fifo_size / 2 - 1) |
-			TX_WMARK(fifo_size / 2);
+	if (host->fifoth_val) {
+		dwmci_writel(host, DWMCI_FIFOTH, host->fifoth_val);
 	}
-	dwmci_writel(host, DWMCI_FIFOTH, host->fifoth_val);
 
 	dwmci_writel(host, DWMCI_CLKENA, 0);
 	dwmci_writel(host, DWMCI_CLKSRC, 0);