pm2fb: source code improvements

This patch concentrates on source compacting, simplification and more
conformance to kernel coding standards.
The major changes:
- RD32() and WR() functions are merged into pm2_RD() and pm2_WR()
- conditional (with switch()) RDAC functions are separated in two
unconditional ones
- the conditional pm2fb_block_op() function is merged into pm2fb_fillrect()
and pm2fb_copyarea()
- WAIT_FIFO() values are corrected

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>