Use SHAs in SRCREV, not tag names

Using tag names in SRCREVs means a network lookup on every parse, and unreproducible builds as the tag might move. These SRCREVs are using tag names:

recipes-devtools/ethos-u-vela/ethos-u-vela-4.4.0-src.inc:SRCREV ?= "4.4.0"
recipes-kernel/arm-npu-ethosu/arm-npu-ethosu-25.05-src.inc:SRCREV_ethosu_driver ?= "25.05"