x86/msr: Fix wr/rdmsr_safe_regs_on_cpu() prototypes

gcc-11 warns about mismatched prototypes here:

  arch/x86/lib/msr-smp.c:255:51: error: argument 2 of type ‘u32 *’ {aka ‘unsigned int *’} declared as a pointer [-Werror=array-parameter=]
    255 | int rdmsr_safe_regs_on_cpu(unsigned int cpu, u32 *regs)
        |                                              ~~~~~^~~~
  arch/x86/include/asm/msr.h:347:50: note: previously declared as an array ‘u32[8]’ {aka ‘unsigned int[8]’}

GCC is right here - fix up the types.

[ mingo: Twiddled the changelog. ]

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210322164541.912261-1-arnd@kernel.org