fix CONFIG_SERVICE_MMC_FABRIC_SD_EMMC_DEMUX_SELECT_PRESENT option

[felixn]

Description

CONFIG_SERVICE_MMC_FABRIC_SD_EMMC_DEMUX_SELECT_PRESENT had no function, since a (similarly named) define was used instead.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Build with CONFIG_SERVICE_MMC_FABRIC_SD_EMMC_DEMUX_SELECT_PRESENT=y -> SD/eMMC Muxing is used
• Build with CONFIG_SERVICE_MMC_FABRIC_SD_EMMC_DEMUX_SELECT_PRESENT=n -> SD/eMMC Muxing is not used

Test Configuration:

• Reference design release: v2023.06
• Hardware: mpfs-icicle-kit-es
• HSS version: v2023.06
• Bare metal examples version: -
• Buildroot / Yocto release: -

Checklist:

• I have reviewed my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have tested that my fix is effective or that my feature works
• I have added a maintainers file for any new board support