cnss: Sysfs support to test BMI Commands

QCA6180 supports various BMI commands which are not needed for
the wlan BMI Phase.
To verify all the BMI Commands add support to test them on need.

Test: echo 0x09 to fw_image_setup to enable bmi testing.

Commands:
BMI_NO_COMMAND, BMI_WRITE_MEMORY, BMI_READ_MEMORY,
BMI_EXECUTE, BMI_GET_TARGET_INFO, BMI_DONE

Change-Id: Ifa2ba0d53b0123e69b3d683c68cd0c773be26353
Signed-off-by: Komal Seelam <kseelam@codeaurora.org>