bus: mhi: core: Use macros for execution environment features

The implementation for execution environment specific functionality
is spread out. Use macros that help determine the paths to be taken.

Link: https://lore.kernel.org/r/1636409978-31847-1-git-send-email-quic_bbhatt@quicinc.com
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20211216081227.237749-4-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>