flash: complete CONFIG_SYS_NO_FLASH move with renaming

We repeated partial moves for CONFIG_SYS_NO_FLASH, but this is
not completed. Finish this work by the tool.

During this move, let's rename it to CONFIG_MTD_NOR_FLASH.
Actually, we have more instances of "#ifndef CONFIG_SYS_NO_FLASH"
than those of "#ifdef CONFIG_SYS_NO_FLASH".  Flipping the logic will
make the code more readable.  Besides, negative meaning symbols do
not fit in obj-$(CONFIG_...) style Makefiles.

This commit was created as follows:

[1] Edit "default n" to "default y" in the config entry in
    common/Kconfig.

[2] Run "tools/moveconfig.py -y -r HEAD SYS_NO_FLASH"

[3] Rename the instances in defconfigs by the following:
  find . -path './configs/*_defconfig' | xargs sed -i \
  -e '/CONFIG_SYS_NO_FLASH=y/d' \
  -e 's/# CONFIG_SYS_NO_FLASH is not set/CONFIG_MTD_NOR_FLASH=y/'

[4] Change the conditionals by the following:
  find . -name '*.[ch]' | xargs sed -i \
  -e 's/ifndef CONFIG_SYS_NO_FLASH/ifdef CONFIG_MTD_NOR_FLASH/' \
  -e 's/ifdef CONFIG_SYS_NO_FLASH/ifndef CONFIG_MTD_NOR_FLASH/' \
  -e 's/!defined(CONFIG_SYS_NO_FLASH)/defined(CONFIG_MTD_NOR_FLASH)/' \
  -e 's/defined(CONFIG_SYS_NO_FLASH)/!defined(CONFIG_MTD_NOR_FLASH)/'

[5] Modify the following manually
  - Rename the rest of instances
  - Remove the description from README
  - Create the new Kconfig entry in drivers/mtd/Kconfig
  - Remove the old Kconfig entry from common/Kconfig
  - Remove the garbage comments from include/configs/*.h

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