x86_32: remove the useless NR_syscalls macro

This is against current x86.git.

The size of the system call table for 32-bit x86 kernels is obtained by
compile-time calculation of the sys_call_table array, not from the value,
which the NR_syscalls macro expands to. This trivial patch removes the
fossil macro.

Manually tested by grepping the x86 files for the "NR_syscalls" string.
No relevant use cases found.

Build-tested using allyesconfig, allnoconfig and a couple of randconfig
instances. All builds successfully finished.

Runtime test performed using a stripped-down Debian-ish config. The system
booted successfully.

Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>