boot/optee-os/optee-os.mk: fix 'PLATFORM' typo

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
(cherry picked from commit 7bd00d5506e8572f316a9b742b78039e0743d86b)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/optee-os/optee-os.mk

@@ -65,7 +65,7 @@ OPTEE_OS_MAKE_OPTS += \
 	CFG_ARM32_core=y
 endif
 
-# Get mandatory PLAFORM and optional PLATFORM_FLAVOR and additional
+# Get mandatory PLATFORM and optional PLATFORM_FLAVOR and additional
 # variables
 OPTEE_OS_MAKE_OPTS += PLATFORM=$(call qstrip,$(BR2_TARGET_OPTEE_OS_PLATFORM))
 ifneq ($(call qstrip,$(BR2_TARGET_OPTEE_OS_PLATFORM_FLAVOR)),)