x86/bugs: Fix return type of spectre_bhi_state()

The definition of spectre_bhi_state() incorrectly returns a const char
* const. This causes the a compiler warning when building with W=1:

 warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
 2812 | static const char * const spectre_bhi_state(void)

Remove the const qualifier from the pointer.

Fixes: ec9404e ("x86/bhi: Add BHI mitigation knob")
Reported-by: Sean Christopherson <[email protected]>
Signed-off-by: Daniel Sneddon <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Daniel Sneddon

arch/x86/kernel/cpu/bugs.c

@@ -2809,7 +2809,7 @@ static char *pbrsb_eibrs_state(void)
 	}
 }
 
-static const char * const spectre_bhi_state(void)
+static const char *spectre_bhi_state(void)
 {
 	if (!boot_cpu_has_bug(X86_BUG_BHI))
 		return "; BHI: Not affected";