spi: Replace spi_pcpu_stats_totalize() macro by a C function

spi_pcpu_stats_totalize() is a rather large macro, and is instantiated
28 times, causing a large amount of duplication in the amount of
generated code.

Reduce the duplication by replacing spi_pcpu_stats_totalize() by a real
C function, and absorb all other common code from
spi_statistics_##name##_show().  As (a) the old "field" parameter was
the name of a structure member, which cannot be passed to a function,
and (b) passing a pointer to the member is also not an option, due to
the loop over all possible CPUs, the "field" parameter is replaced by an
"offset" parameter, pointing to a location within the structure.

This reduces kernel size by ca. 4 KiB (on arm32 and arm64).

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/cb7690d9d04c06eec23dbb98fbb5444082125cff.1677594432.git.geert+renesas@glider.be


Signed-off-by: Mark Brown <broonie@kernel.org>