optee-os: don't override upstream TA_LOG_LEVEL setting

Aside from diverging from upstream, appending such a change it at the end of
oe_runmake makes it hard to override it in a bbappend.

This value does not seem to be inherited in TA builds, and
eg. optee-examples do use the the values set in their individual
Makefiles.  Setting this to 0 however seems to cause the TA traces not
to be relayed to the console, so the examples end up less
self-illustrative than they should.

This patch restores the upstream choice, while allowing downstream layers to
choose to set it to zero if they wish to do so.

Signed-off-by: Yann Dirson <yann@blade-group.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-security/optee/optee-os.inc

@@ -38,7 +38,7 @@ LD[unexport] = "1"
 do_configure[noexec] = "1"
 
 do_compile() {
-    oe_runmake -C ${S} all CFG_TEE_TA_LOG_LEVEL=0
+    oe_runmake -C ${S} all
 }
 do_compile[cleandirs] = "${B}"