optee-os: Update SRCREV for OP-TEE TRNG in J784S4

Update the SRCREV to the commit when sa3ul support was
added in upstream OP-TEE for J784S4 platform to access rng.

Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Ryan Eatmon <reatmon@ti.com>

recipes-security/optee/optee-os_%.bbappend

@@ -1,5 +1,5 @@
 PV_ti-soc = "3.18.0+git${SRCPV}"
-SRCREV_ti-soc = "8e155bae3a5eb9d1a3ed9260bd7281a7a35f5086"
+SRCREV_ti-soc = "6bf4a81a8f5388e6cb6b1d7e8ebe57c5089c0954"
 SRC_URI_ti-soc = "git://github.com/OP-TEE/optee_os.git;protocol=https"
 
 DEPENDS_append_ti-soc = " python3-cryptography-native"