net: smsc911x: don't artificially limit build

Currently the SMSC911X driver may only be built for a specific set of
architectures, being limited to do so by a Kconfig depends line. This
means that if a platform wishes to use the driver, its architecture must
be added to the list explicitly, introducing pointless churn.

This may have been due to the driver's use of the {read,write}s{b,w,l}
functions, which have since been replaced with the more standard
io{read,write}{8,16,32}_rep. We can instead depend on HAS_IOMEM, which
should prevent build issues while allowing the driver to be built for
currently unlisted architectures, including x86 and arm64.

This patch removes the explicit list of architectures from the driver's
depend line, and replaces it with a dependency on HAS_IOMEM.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>