dma-mapping: add DMA_xxBIT_MASK to feature-removal-schedule.txt

DMA_xxBIT_MASK macros were marked as deprecated in June 2009. One more
year is long enough, I think.

Signed-off-by: FUJITA Tomonori <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/feature-removal-schedule.txt

···
 Who:	FUJITA Tomonori <[e-mail]>
 
 ----------------------------
+
+What: 	DMA_xxBIT_MASK macros
+When:	Jun 2011
+Why:	DMA_xxBIT_MASK macros were replaced with DMA_BIT_MASK() macros.
+Who:	FUJITA Tomonori <[e-mail]>
+
+----------------------------
+