Revert "Revert "soc: qcom: glink_bgcom_xprt: Add TX short command"".

This reverts commit 4416fe63.

TX short command is used to send data smaller than 16 bytes,
over FIFO instead of AHB.
Added TX short command.

Change-Id: I28b62852e6b44e053fe53c8c25c40adb69281a50
Signed-off-by: shwetha paalavalasa <spaala@codeaurora.org>