Documentation: arm: marvell: Fix dead link to Armada 37xx Product Brief

Signed-off-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20210125141341.32200-1-pali@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/arm/marvell.rst

@@ -183,7 +183,7 @@ EBU Armada family ARMv8
 	http://www.marvell.com/embedded-processors/armada-3700/
 
   Product Brief:
-	http://www.marvell.com/embedded-processors/assets/PB-88F3700-FNL.pdf
+	http://www.marvell.com/content/dam/marvell/en/public-collateral/embedded-processors/marvell-embedded-processors-armada-37xx-product-brief-2016-01.pdf
 
   Hardware Spec:
 	http://www.marvell.com/content/dam/marvell/en/public-collateral/embedded-processors/marvell-embedded-processors-armada-37xx-hardware-specifications-2019-09.pdf