Platform: Remove unused parameter

copy_size is an unused parameter in one of the OTP template
files so better to remove it to silence compiler warnings.

Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
Change-Id: I03f4c9433b93b37e4ad366758c64ac1929e0ce06
diff --git a/platform/ext/common/template/otp_flash.c b/platform/ext/common/template/otp_flash.c
index df630f4..64c3858 100644
--- a/platform/ext/common/template/otp_flash.c
+++ b/platform/ext/common/template/otp_flash.c
@@ -116,7 +116,6 @@
 {
     enum tfm_plat_err_t err = TFM_PLAT_ERR_SUCCESS;
     size_t value_size;
-    size_t copy_size;
     uint8_t buffer[in_len];
     size_t idx;