mmc: core: Fix DT documentation of eMMC high-speed DDR 1.8/1.2V bindings

Currently the documentation doesn't match the code in mmc_of_parse. This
patch rectifies this.
Signed-off-by: NPeter Griffin <peter.griffin@linaro.org>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/mmc.txt

@@ -34,8 +34,8 @@ Optional properties:
 - cap-power-off-card: powering off the card is safe
 - cap-sdio-irq: enable SDIO IRQ signalling on this interface
 - full-pwr-cycle: full power cycle of the card is supported
-- mmc-highspeed-ddr-1_8v: eMMC high-speed DDR mode(1.8V I/O) is supported
-- mmc-highspeed-ddr-1_2v: eMMC high-speed DDR mode(1.2V I/O) is supported
+- mmc-ddr-1_8v: eMMC high-speed DDR mode(1.8V I/O) is supported
+- mmc-ddr-1_2v: eMMC high-speed DDR mode(1.2V I/O) is supported
 - mmc-hs200-1_8v: eMMC HS200 mode(1.8V I/O) is supported
 - mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported
 - mmc-hs400-1_8v: eMMC HS400 mode(1.8V I/O) is supported