asm-generic: provide entirely generic nommu uaccess

Move the code to implement uaccess using memcpy or direct loads and
stores to asm-generic/uaccess.h and make it selectable kconfig option.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
5 files changed