mips: remove extraneous asm-generic/iomap.h include

mips: remove extraneous asm-generic/iomap.h include

When this file is included before defining readq(), it misses the
declarations for a couple of functions that now become unusable:

lib/iomap.c:156:5: warning: no previous prototype for 'ioread64_lo_hi' [-Wmissing-prototypes]
lib/iomap.c:163:5: warning: no previous prototype for 'ioread64_hi_lo' [-Wmissing-prototypes]
lib/iomap.c:170:5: warning: no previous prototype for 'ioread64be_lo_hi' [-Wmissing-prototypes]
lib/iomap.c:178:5: warning: no previous prototype for 'ioread64be_hi_lo' [-Wmissing-prototypes]
lib/iomap.c:264:6: warning: no previous prototype for 'iowrite64_lo_hi' [-Wmissing-prototypes]
lib/iomap.c:272:6: warning: no previous prototype for 'iowrite64_hi_lo' [-Wmissing-prototypes]
lib/iomap.c:280:6: warning: no previous prototype for 'iowrite64be_lo_hi' [-Wmissing-prototypes]
lib/iomap.c:288:6: warning: no previous prototype for 'iowrite64be_hi_lo' [-Wmissing-prototypes]

The file is included again later from asm-generic/io.h, so dropping the initial
include statement makes it do the right thing, both for avoiding the warning
and for actually providing these functions.

Link: https://lkml.kernel.org/r/20231204115710.2247097-17-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Stephen Rothwell <sfr@rothwell.id.au>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>