refactor: Refactor the MMC documentation in UG-Memory

Fix the MMC documentation in UG-Memory. The file has been patched
up in a way that is uneccessarily difficult to browse. Fix up the
documentation sections and whitespace.

While we are here add additional necessary sections for MMC.

Signed-off-by: Judith Mendez <[email protected]>

Author: jmenti

source/linux/Foundational_Components/Tools/Flash_via_DFU.rst

@@ -250,7 +250,7 @@ following value:
 - Use `part` for raw flashing to a partition defined in GPT or DOS partition table. If `part`
   is used, both `hwpart` & `partid` are required.
 - It should be noted using `part` requires a partition table already in the respective
-  hardware partition in eMMC. For steps refer :ref:`partitioning-eMMC-from-uboot`.
+  hardware partition in eMMC. For steps refer :ref:`create-partitions-in-emmc-uda-from-linux`.
 
 In the config file, specify operation as