disk: sdhc: use the multiple block transfer for writing

The sdhc_spi_write_multi function is sending the CMD25
for multiple block write operation on the SD card
instead of looping the CMD24. This is improving
the transfer speed compared to the sdhc_spi_write function
when the nb of blocks to write is significant (more than 2).

Signed-off-by: Francois Ramu <francois.ramu@st.com>