platform: msm_shared: Remove static keyword for read_der_message_length()

Enabling read_der_message_length() to be called outside of boot_verifier.c

Change-Id: Ic0483232faefdf79092739429524a830881fdf85
diff --git a/platform/msm_shared/include/boot_verifier.h b/platform/msm_shared/include/boot_verifier.h
index 485cc3c..38bcf17 100644
--- a/platform/msm_shared/include/boot_verifier.h
+++ b/platform/msm_shared/include/boot_verifier.h
@@ -179,4 +179,5 @@
 bool boot_verify_compare_sha256(unsigned char *image_ptr,
 		unsigned int image_size, unsigned char *signature_ptr, RSA *rsa);
 KEYSTORE *boot_gerity_get_oem_keystore();
+uint32_t read_der_message_length(unsigned char* input, unsigned sz);
 #endif