audio-kernel: Assign target name msmsteppe for sm6150

Use msmsteppe target name instead of macro as macro
cannot be used in target rc file.

Signed-off-by: Ramprasad Katkam <katkam@codeaurora.org>
Change-Id: I0f3ec299b28b7dfd9f8ac9985eea0c22a4611f9e