drm/i915: fix i915_globals_exit() section mismatch error

Fix modpost Section mismatch error in i915_globals_exit().
Since both an __init function and an __exit function can call
i915_globals_exit(), any function that i915_globals_exit() calls
should not be marked as __init or __exit. I.e., it needs to be
available for either of them.

WARNING: modpost: vmlinux.o(.text+0x8b796a): Section mismatch in reference from the function i915_globals_exit() to the function .exit.text:__i915_globals_flush()
The function i915_globals_exit() references a function in an exit section.
Often the function __i915_globals_flush() has valid usage outside the exit section
and the fix is to remove the __exit annotation of __i915_globals_flush.

ERROR: modpost: Section mismatches detected.
Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.

Fixes: 1354d830

 ("drm/i915: Call i915_globals_exit() if pci_register_device() fails")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210804204147.2070-1-rdunlap@infradead.org