powerpc/32: Remove powerpc specific definition of 'ptrdiff_t'

For unknown reason, old commit d27dfd388715 ("Import pre2.0.8")
changed 'ptrdiff_t' from 'int' to 'long'.

GCC expects it as 'int' really, and this leads to the following
warning when building KFENCE:

CC mm/kfence/report.o
In file included from ./include/linux/printk.h:7,
from ./include/linux/kernel.h:16,
from mm/kfence/report.c:10:
mm/kfence/report.c: In function 'kfence_report_error':
./include/linux/kern_levels.h:5:18: warning: format '%td' expects argument of type 'ptrdiff_t', but argument 6 has type 'long int' [-Wformat=]
5 | #define KERN_SOH "\001" /* ASCII Start Of Header */
| ^~~~~~
./include/linux/kern_levels.h:11:18: note: in expansion of macro 'KERN_SOH'
11 | #define KERN_ERR KERN_SOH "3" /* error conditions */
| ^~~~~~~~
./include/linux/printk.h:343:9: note: in expansion of macro 'KERN_ERR'
343 | printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__)
| ^~~~~~~~
mm/kfence/report.c:213:3: note: in expansion of macro 'pr_err'
213 | pr_err("Out-of-bounds %s at 0x%p (%luB %s of kfence-#%td):\n",
| ^~~~~~

<asm-generic/uapi/posix-types.h> defines it as 'int', and
defines 'size_t' and 'ssize_t' exactly as powerpc do, so
remove the powerpc specific definitions and fallback on
generic ones.

Signed-off-by: Christophe Leroy <[e-mail]>
Acked-by: Segher Boessenkool <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/e43d133b[e-mail]

arch/powerpc/include/uapi/asm/posix_types.h

···
 typedef unsigned long	__kernel_old_dev_t;
 #define __kernel_old_dev_t __kernel_old_dev_t
 #else
-typedef unsigned int	__kernel_size_t;
-typedef int		__kernel_ssize_t;
-typedef long		__kernel_ptrdiff_t;
-#define __kernel_size_t __kernel_size_t
-
 typedef short		__kernel_ipc_pid_t;
 #define __kernel_ipc_pid_t __kernel_ipc_pid_t
 #endif