Making virt_to_pfn() a static inline taking a strongly typed
(const void *) makes the contract of a passing a pointer of that
type to the function explicit and exposes any misuse of the
macro virt_to_pfn() acting polymorphic and accepting many types
such as (void *), (unitptr_t) or (unsigned long) as arguments
without warnings.

Move the function down in the file so __pa() exists in our
scope, and it compiles. This in turn requires moving __pa()
as it depends on __virt_to_phys() that was below. (Lazy macro
evaluation conflicts with strict function ordering.)

Make a symmetric change to pfn_to_virt() so we have type
checking both ways.

Due to this the <asm/page.h> file being included into some
assembly files, some further inclusion guards are needed
to make sure assembly keeps compiling.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230808-virt-to-phys-microblaze-v1-1-e6df710fe0a1@linaro.orgSigned-off-by: Michal Simek <michal.simek@amd.com>