portability: cmsis: Clarify Kconfig set max limit on dynamic objects

Clarify that all max limit on RTOS objects set by Kconfig only apply
to objects whose control blocks were dynamically allocated. The
CMSIS-RTOSv2 impl layer itself does not restrict the number of
statically created RTOS objects.

Signed-off-by: Utsav Munendra <utsavm@meta.com>