firmware: fix SoC variant in help text of FIRMWARE_IMX93_OPTEE #20

Job	Run time
labgrid-pytest (arm, test/arm/*@multi_v7_defconfig.yaml, multi_v7_defconfig)	3m 1s
labgrid-pytest (arm, test/arm/multi_v8_defconfig.yaml, multi_v8_defconfig)	2m 12s
labgrid-pytest (mips, test/mips/qemu-malta_defconfig.yaml, qemu-malta_defconfig)	1m 41s
labgrid-pytest (mips, test/mips/qemu-malta64el_defconfig.yaml, qemu-malta64el_defconfig)	1m 22s
labgrid-pytest (openrisc, test/openrisc/generic_defconfig.yaml, generic_defconfig)	1m 32s
labgrid-pytest (x86, test/x86/efi_defconfig.yaml, efi_defconfig)	1m 18s
labgrid-pytest (riscv, test/riscv/qemu@virt32_defconfig.yaml, virt32_defconfig)	1m 33s
labgrid-pytest (riscv, test/riscv/qemu-virt64@rv64i_defconfig.yaml, rv64i_defconfig)	1m 48s
	14m 27s

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