The current BL33 size is large enough for U-Boot, but we need to
increase the limit to use other boot loaders such as edk2.

Increase the buffer size used for GZIP decompression too.

 BL33 max size (UNIPHIER_BL33_MAX_SIZE):  1MB -> 8MB
 GZIP buffer (UNIPHIER_IMAGE_BUF_SIZE):   1MB -> 8MB

Increasing the block buffer size (UNIPHIER_BLOCK_BUF_SIZE) is not
required, but I increased it too to make it work more efficiently.

Change-Id: I4fa6d795bed9ab9ada7f8f616c7d47076139e3a8
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>