firmware: qcom_scm: Add missing extern specifier

Commit 3a99f12 ("firmware: qcom: scm: Introduce pas_metadata
context") left out the `extern` specifier for the API it introduced, so
add it.

Signed-off-by: Guru Das Srinagesh <quic_gurus@quicinc.com>
Link: https://lore.kernel.org/r/bce25c8e215f7cfc7b0780d6965d09f5efe1cc5f.1690503893.git.quic_gurus@quicinc.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: Guru Das Srinagesh

include/linux/firmware/qcom/qcom_scm.h

@@ -75,7 +75,7 @@ struct qcom_scm_pas_metadata {
 extern int qcom_scm_pas_init_image(u32 peripheral, const void *metadata,
 				   size_t size,
 				   struct qcom_scm_pas_metadata *ctx);
-void qcom_scm_pas_metadata_release(struct qcom_scm_pas_metadata *ctx);
+extern void qcom_scm_pas_metadata_release(struct qcom_scm_pas_metadata *ctx);
 extern int qcom_scm_pas_mem_setup(u32 peripheral, phys_addr_t addr,
 				  phys_addr_t size);
 extern int qcom_scm_pas_auth_and_reset(u32 peripheral);