ARM: 8587/1: dma-mapping: Use %zu for printing a size_t variable

According to Documentation/printk-formats.txt when printing
a size_t variable we should use %zu or %zx format specifiers.

As we are printing a memory size value, we should better use %zu
in this case.

Reported-by: Frank Mori Hess <fmh6jj@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>