serial: Kconfig: Add separate console Kconfig for msm_geni_serial

Add a separate Kconfig item for console functionality of the
msm_geni_serial.

Change-Id: I6f06ee32d09728b855076a1ccdae9dbbb2fd0a84
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>