etnaviv: Remove duplicate initializers

etnaviv: Remove duplicate initializers

Fix initializer-overrides warnings.

../src/gallium/drivers/etnaviv/etnaviv_compiler.c:62:29: warning: initializer overrides prior initialization of this subobject [-Winitializer-overrides]
   62 |       .lower_extract_byte = true,
      |                             ^~~~
../src/gallium/drivers/etnaviv/etnaviv_compiler.c:63:29: warning: initializer overrides prior initialization of this subobject [-Winitializer-overrides]
   63 |       .lower_extract_word = true,
      |                             ^~~~

Fixes: 9dc4ee91215 ("etnaviv: lower (un)pack_{2x16,2x32}_split and extract_{byte,word}")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <cgmeiner@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26773>
(cherry picked from commit f5d08bdf4e3a0e75a846b76889e234b7c9bbd754)