stmhal/hal/src/stm32f4xx_hal_sd.c: fix SDHC card capacity
stmhal/sdcard.c: add pyb.SD.write
stmhal: Change 64-bit arithmetic to 32-bit for SD card block addressing.

By measuring SD card addresses in blocks and not bytes, one can get away
with using 32-bit numbers.

This patch also uses proper atomic lock/unlock around SD card
read/write, adds SD.info() function, and gives error code for failed
read/writes.