Add GOMIPS=softfloat for mips architecture to support GL-AR300M16-EXT

[Copilot]

The GL-AR300M16-EXT (QCA9531/mips_24kc) lacks hardware FPU. Binaries built without GOMIPS=softfloat are incompatible.

Changes

• Extended build condition to apply GOMIPS=softfloat to both mips and mipsle architectures (previously only mipsle)

- if [[ "${{ matrix.platform }}" == "mipsle" ]]; then
+ if [[ "${{ matrix.platform }}" == "mips" || "${{ matrix.platform }}" == "mipsle" ]]; then
    CGO_ENABLED=0 GOOS=${{ matrix.os }} GOARCH=${{ matrix.platform }} GOMIPS=softfloat \

This ensures binaries work on MIPS devices without hardware floating-point units.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>GL-AR300M16-EXT Support</issue_title>
<issue_description>The produced tiny binaries are incompatible, it needs GOMIPS=softfloat added.

</issue_description>

<agent_instructions>Create a new branch called "gl-ar300m16-ext-support", make sure to check if the built binary is executable on the target system.

Information based on the OpenWrt Wiki for the GL-AR300M16-EXT
Target:ath79
Subtarget:generic
Package architecture:mips_24kc
CPU:Qualcomm Atheros QCA9531</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes GL-AR300M16-EXT Support #17

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