drivers: partition: support different block size

The block size of some storage device is 4096-byte long, such as UFS. But
PARTITION_BLOCK_SIZE is defined as 512-byte long. So replace it by
PLAT_PARTITION_BLOCK_SIZE. Make it configurable in platform.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Change-Id: Iada05f7c646d0a0f2c0d3b8545540b3cb7153de3
diff --git a/include/drivers/partition/gpt.h b/include/drivers/partition/gpt.h
index 3ae160f..d923e95 100644
--- a/include/drivers/partition/gpt.h
+++ b/include/drivers/partition/gpt.h
@@ -10,9 +10,9 @@
 #include <drivers/partition/partition.h>
 
 #define PARTITION_TYPE_GPT		0xee
-#define GPT_HEADER_OFFSET		PARTITION_BLOCK_SIZE
+#define GPT_HEADER_OFFSET		PLAT_PARTITION_BLOCK_SIZE
 #define GPT_ENTRY_OFFSET		(GPT_HEADER_OFFSET +		\
-					 PARTITION_BLOCK_SIZE)
+					 PLAT_PARTITION_BLOCK_SIZE)
 #define GUID_LEN			16
 
 #define GPT_SIGNATURE			"EFI PART"