spi: spi-geni-qcom: Introduce new driver for GENI based core

Introduce a new SPI driver for Qualcomm Techonologies Inc's (QTI) GENI
based serial engine cores.
The driver can currently do FIFO mode of data transfer, here the driver
writes/reads data to/from the HW FIFO directly.

Change-Id: I3d14bdf0acf6a8c1f7772d8f3f4e1cd17f44c78e
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>