Add a new CONFIG_MALLOC_DEBUG option to control malloc() debugging
features. This replaces the direct UNIT_TEST check and allows enabling
malloc debugging independently of whether UNIT_TEST is enabled.
The option defaults to y when UNIT_TEST is enabled, preserving existing
behaviour. Disable for RISC-V since it seems to have a size limitation.
Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>