Update revision for release tag 3.8.0-rc1

Signed-off-by: Jerome Forissier <jerome@forissier.org>
diff --git a/mk/config.mk b/mk/config.mk
index ff70438..8e638c0 100644
--- a/mk/config.mk
+++ b/mk/config.mk
@@ -116,7 +116,7 @@
 # with limited depth not including any tag, so there is really no guarantee
 # that TEE_IMPL_VERSION contains the major and minor revision numbers.
 CFG_OPTEE_REVISION_MAJOR ?= 3
-CFG_OPTEE_REVISION_MINOR ?= 7
+CFG_OPTEE_REVISION_MINOR ?= 8
 
 # Trusted OS implementation manufacturer name
 CFG_TEE_MANUFACTURER ?= LINARO