mm/Kconfig: remove wrong dependency and explanation for MM_KERNEL_HEAP
mm/Kconfig: remove wrong dependency and explanation for MM_KERNEL_HEAP

CONFIG_MM_KERNEL_HEAP is mandatory so that it should not be turned
off by user and it should not have any dependency. Explanation either
has regacy content.
This commit removes dependencies with PROTECTED_BUILD and KERNEL_BUILD
and remove config description to hide from user.

Signed-off-by: sunghan-chang <c954e25285721d8faa8b1a5c1ae2ef5a35338d32@samsung.com>

Samsung/TizenRT,pillip8282/TizenRT,jeongarmy/TizenRT,pillip8282/TizenRT,jeongchanKim/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,jeongchanKim/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,jsdosa/TizenRT,pillip8282/TizenRT,an4967/TizenRT,junmin-kim/TizenRT,an4967/TizenRT,Samsung/TizenRT,jsdosa/TizenRT,pillip8282/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,an4967/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,jeongchanKim/TizenRT,sunghan-chang/TizenRT,sunghan-chang/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,Samsung/TizenRT,an4967/TizenRT,jsdosa/TizenRT,sunghan-chang/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,jeongarmy/TizenRT,jeongchanKim/TizenRT,jsdosa/TizenRT,sunghan-chang/TizenRT,jeongarmy/TizenRT,junmin-kim/TizenRT,jeongchanKim/TizenRT,jsdosa/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,jsdosa/TizenRT,jeongarmy/TizenRT,an4967/TizenRT,Samsung/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,sunghan-chang/TizenRT,jeongarmy/TizenRT