asm-generic/io.h: Unbork ioremap_np() declaration

It accidentally slipped into the #ifdef for ioremap_uc().

Signed-off-by: Hector Martin <marcan@marcan.st>
Link: https://lore.kernel.org/r/20210409052038.58925-1-marcan@marcan.st

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>