ARM: 6871/1: Use asm-generic/sizes.h

Commit d232b128

 (asm-generic headers: add sizes.h, 2011-01-15)
introduced a generic sizes.h. Use that instead of the ARM specific
version.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>