essl_read_reg() function

Handle of a ``essl`` device.

Address of register to read. For SDIO, Valid address: 0-27, 32-63 (28-31 reserved, return interrupt bits on read). For SPI, see ``essl_spi.h``

Output value read from the register.

Millisecond to wait before timeout, will not wait at all if set to 0-9.