#2 [OPT] remove redundant invalid marking operation

[DongYoung Seo]

ASAST_WritePage() function set invalid flag at the old data block and log block after new data is written at log block.
But There is only one valid page within both data block and log blocks.
So we do not write invalid part to all of the previous out of data pages.

ASAST_WritePage() funtion checks all page mapping information to find page that has newly written page number.

We can remove this redundant search and update operation --> just update page mapping table