mmc: stm32_sdmmc2: cosmetic: rename stm32_sdmmc_bind

Rename stm32_sdmmc_bind to stm32_sdmmc2_bind as all other functions
in SDMMCv2 driver

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Change-Id: Ic51acdfbbba6e971809c1029dd2227038bfe879d