powerpc/vdso: augment VDSO32 functions to support 64 bits build

VDSO64 cacheflush.S datapage.S gettimeofday.S and vgettimeofday.c
are very similar to their VDSO32 counterpart.

VDSO32 counterpart is already more complete than the VDSO64 version
as it supports both PPC32 vdso and 32 bits VDSO for PPC64.

Use compat macros wherever necessary in PPC32 files
so that they can also be used to build VDSO64.

vdso64/note.S is already a link to vdso32/note.S so
no change is required.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c2cbb8f046b7efc251053521dc39b752795e26b7.1642782130.git.christophe.leroy@csgroup.eu