Replaced the GNU-only dsb/isb 0xF operands with the UAL sy form - #729

…AL sy form, so tx_port.h now assembles under IAR as well as GCC and armclang

The inline _tx_thread_system_return_inline implementation in the Cortex-M
tx_port.h headers issued its data and instruction barriers as "dsb 0xF"
and "isb 0xF". A bare hexadecimal operand is a GNU assembler extension.
IAR's inline assembler only accepts the architectural option names, so it
rejected the line with "operand syntax error" and the header could not be
included at all. The block is guarded for GCC, armclang and IAR together,
so every IAR user of an affected port hit this the moment inlining was
left enabled.

Replaced both operands with "sy", the Arm UAL name for the full system
domain and the exact value 0xF encodes. The generated instruction is
unchanged; only the spelling of the operand differs. "sy" is the
canonical form in the Arm Architecture Reference Manual and is accepted
by GNU as, armclang and IAR alike, which is why every reporter converged
on it independently as a local workaround.

The change was applied to the two ports_arch master headers and to all
thirty-two generated or hand-maintained copies under ports, covering the
Cortex-M0, M23, M3, M33, M4, M52, M55, M7 and M85 families across the
ac5, ac6, gnu, iar and keil toolchains.

scripts/check_ports.sh probed for the literal strings "dsb 0xF" and
"isb 0xF" when reporting toolchain divergence within the hand-maintained
M0 and M23 families. Updated the probes to the new spelling so the check
keeps working.

Verified that arm-none-eabi-gcc assembles the new form for every Cortex-M
target the ports cover, and confirmed the regenerated ports match their
masters.

Assisted-by: Copilot (Opus 5) <noreply@github.com>