arm64: Delete the space separator in __emit_inst

Many instances of __emit_inst(x) expand to a directive. In a few places
it is used as a macro argument, e.g.

  arch/arm64/include/asm/sysreg.h
  #define __emit_inst(x)                       .inst (x)

  arch/arm64/include/asm/sysreg.h
  #define SET_PSTATE_PAN(x)            __emit_inst(0xd500401f | PSTATE_PAN | ((!!x) << PSTATE_Imm_shift))

  arch/arm64/kvm/hyp/entry.S
  ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)

Clang integrated assembler parses `.inst (x)` as two arguments passing
to a macro. We delete the space separator so that `.inst(x)` will be
parsed as one argument.

Note, GNU as parsing `.inst (x)` as one argument is unintentional (for
example the x86 backend will parse the construct as two arguments).
See https://sourceware.org/bugzilla/show_bug.cgi?id=25750#c10

Link: ClangBuiltLinux#939
Cc: clang-built-linux@googlegroups.com
Signed-off-by: Fangrui Song <maskray@google.com>

arch/arm64/include/asm/sysreg.h

@@ -49,7 +49,9 @@
 #ifndef CONFIG_BROKEN_GAS_INST
 
 #ifdef __ASSEMBLY__
-#define __emit_inst(x)			.inst (x)
+// The space separator is omitted so that __emit_inst(x) can be parsed as
+// either a directive or a macro argument.
+#define __emit_inst(x)			.inst(x)
 #else
 #define __emit_inst(x)			".inst " __stringify((x)) "\n\t"
 #endif