ARM: dts: qcom: add device tree for Sony Xperia SP

ARM: dts: qcom: add device tree for Sony Xperia SP

Add initial device tree support for the Sony Xperia SP (codename:
sony-huashan), a smartphone based on the Qualcomm MSM8960T SoC.

There are two variants of the Xperia SP, one without LTE and one with
LTE. This device tree should work for both variants, though it has only
been tested on the non-LTE variant.

The following are currently supported:
- Serial console support via gsbi8
- GPIO keys for volume up/down buttons
- PM8921 keypad with camera focus/capture keys
- eMMC (sdcc1) and micro SD card (sdcc3) support
- USB OTG support

Other hardware features are not yet implemented.

Booting notes:
Booting a kernel requires using the Sony ELF boot image format, which
embeds the kernel, ramdisk, RPM firmware, and cmdline. This can be
created using the `mkelf` tool. For example:

  python2 mkelf.py -o boot.img \
    kernel+dtb@0x80208000 \
    ramdisk.img@0x81900000 \
    RPM.bin@0x00020000,rpm \
    cmdline.txt@cmdline

The resulting `boot.img` can then be flashed via fastboot. A detailed
guide, including an alternative method, is available at:
https://wiki.postmarketos.org/wiki/Sony_Xperia_SP_(sony-huashan)

Signed-off-by: Antony Kurniawan Soemardi <linux@smankusors.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250623-msm8960-sdcard-v2-5-340a5e8f7df0@smankusors.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>