meta-lxatac-bsp: linux-lxatac: upgrade to 6.6

[hnez]

umpf tag is now: 6.6/customers/lxa/lxatac/20231106-1 The tag includes the following topic branches:

• v6.6/customers/lxa/lxatac
• v6.6/topic/pwm-stm32
• v6.6/topic/pwm-backlight
• v6.6/topic/tty-trigger

Starting with this kernel version the LXA TAC base devicetree is mainline \o/ and we no longer have to add it here as a patch. The TI LMP92064 buffering support also made it mainline.

I've also moved back from fetching the sources via git to tarballs. The benefits are:

• An uname -a does not show the kernel version as -dirty anymore (caused by the patches we applied to the git repository)
• I get less confused when updating the PV does not do anything.
• The initial download is a lot smaller.

[hnez]

Assigned @ukleinek because he knows a lot about new defconfig flags, making him a good reviewer for this.

[hnez]

Closed in favor of #101, which does both the 6.5 -> 6.6 and the 6.6 -> 6.7 update.