heap: simplify heap size calculation

[lyakh]

Fixes two issues:

1. remove confusingly named CONFIG_SOF_ZEPHYR_VIRTUAL_HEAP_SIZE since it isn't used for virtual heap but for a traditional one - not using run-time memory mapping.
2. instead of adding CONFIG_SOF_ZEPHYR_VIRTUAL_HEAP_SIZE switch back to using CONFIG_SOF_ZEPHYR_HEAP_SIZE also when CONFIG_VIRTUAL_HEAP is selected by just adjusting its value.

[Copilot]

Pull request overview

Simplifies heap sizing under VIRTUAL_HEAP by removing the separate “virtual heap size” Kconfig symbol and relying on SOF_ZEPHYR_HEAP_SIZE (with an adjusted default) instead.

Changes:

• Removed SOF_ZEPHYR_VIRTUAL_HEAP_SIZE Kconfig option and the HEAPMEM_SIZE override in alloc.c when CONFIG_VIRTUAL_HEAP is enabled.
• Added a VIRTUAL_HEAP-specific default for SOF_ZEPHYR_HEAP_SIZE.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
zephyr/lib/alloc.c	Drops the conditional HEAPMEM_SIZE redefinition for CONFIG_VIRTUAL_HEAP.
zephyr/Kconfig	Removes the dedicated virtual heap size symbol and sets a smaller default heap size when VIRTUAL_HEAP is enabled.

Comments suppressed due to low confidence (2)

zephyr/lib/alloc.c:1

• With the HEAPMEM_SIZE override removed under CONFIG_VIRTUAL_HEAP, this block now relies on HEAPMEM_SIZE being defined correctly elsewhere. To make the contract explicit and avoid future regressions from include/macro ordering changes, consider defining HEAPMEM_SIZE in one place (or using CONFIG_SOF_ZEPHYR_HEAP_SIZE directly at the allocation site) rather than depending on implicit prior definitions.

// SPDX-License-Identifier: BSD-3-Clause

zephyr/Kconfig:1

• Now that SOF_ZEPHYR_HEAP_SIZE changes default behavior under VIRTUAL_HEAP, the help text for SOF_ZEPHYR_HEAP_SIZE should be updated to capture the guidance that was previously documented under SOF_ZEPHYR_VIRTUAL_HEAP_SIZE (e.g., that this value is reduced when buffers are virtualized and must still respect physical memory limits / DT-defined memory). This avoids configuration confusion after removing the dedicated symbol.

config SOF_FULL_ZEPHYR_APPLICATION

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