(feat) Add basic mimxrt support.

[andrewleech]

I'm working on getting LVGL working cleanly on the NXP 1170 EVK with a LVGL v9 compatible driver in progress here: https://github.com/andrewleech/imxrt1170_display_driver

These minimal changes to the LVGL bindings files enables the build environment to enable port specific features more easily.

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Summary by cubic

Add basic NXP i.MX RT (mimxrt) support by enabling port-specific LVGL GPU/PXP configuration and wiring build flags for the mimxrt port. This allows LVGL v9 to run on the RT1170 EVK with PXP acceleration.

• New Features
  • Detect the active port in micropython.mk and add a mimxrt block that enables LV_USE_PXP, LV_USE_DRAW_PXP, LV_USE_GPU_NXP_PXP, and LV_USE_GPU_NXP_PXP_AUTO_INIT.
  • Make LV_USE_DRAW_VGLITE and LV_USE_PXP overridable in lv_conf.h so ports can turn these on without editing the config.
  • Suppress specific compiler warnings for PXP files to keep the mimxrt build clean.

^{Written for commit 09a4d3ce70d7ba7d35e9f801a4c84a39b283447f. Summary will update automatically on new commits.}