freedreno/ir3: Add missing ir3_nir_lower_tex_prefetch.c to Android.mk

This file is created in 2a0d45ae but
addition to android makefiles was omitted. It breaks the build with
missing references which are defined in this file.
List the file in ir3_SOURCES to make the build succeed.

Signed-off-by: Marijn Suijten <marijns95@gmail.com>
49 jobs for !2392 with ir3-missing-file in 21 minutes and 39 seconds (queued for 4 seconds)
merge request
Name Stage Failure
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lima-test:armhf Test
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lima-test:arm64 Test
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