u-boot-ti: Use SRCREV to get short commit ID

Due to recent security update in git, we are
not able to fetch revision currently using existing method:
https://github.blog/2022-04-12-git-security-vulnerability-announced/

So instead, use the SRCREV to parse the short commit ID
and set the UBOOT_LOCALVERSION variable.

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
Signed-off-by: Ryan Eatmon <reatmon@ti.com>

recipes-bsp/u-boot/u-boot-ti.inc

@@ -1,14 +1,6 @@
 # UBOOT_LOCALVERSION can be set to add a tag to the end of the
 # U-boot version string.  such as the commit id
-def get_git_revision(p):
-    import subprocess
-
-    try:
-        return subprocess.Popen("git rev-parse HEAD 2>/dev/null ", cwd=p, shell=True, stdout=subprocess.PIPE, universal_newlines=True).communicate()[0].rstrip()
-    except OSError:
-        return None
-
-UBOOT_LOCALVERSION = "-g${@get_git_revision('${S}').__str__()[:10]}"
+UBOOT_LOCALVERSION = "-g${@d.getVar("SRCREV", False).__str__()[:10]}"
 
 UBOOT_SUFFIX ?= "img"
 SPL_BINARY ?= "MLO"