Remove gcc-specific optimizations

These flags were added for gcc, but are always stripped out when
compiling for clang.  Since gcc is barely used, removed them.

Bug: 68855788
Bug: 68947919
Test: m checkbuild
Change-Id: Iae2bda9808dd9499848ce145ccdf71c4c490b80e

cc/config/mips64_device.go

@@ -22,17 +22,10 @@ import (
 
 var (
 	mips64Cflags = []string{
-		"-fomit-frame-pointer",
-		"-funswitch-loops",
 		"-Umips",
 
 		// Help catch common 32/64-bit errors.
 		"-Werror=implicit-function-declaration",
-
-		// TARGET_RELEASE_CFLAGS
-		"-fgcse-after-reload",
-		"-frerun-cse-after-loop",
-		"-frename-registers",
 	}
 
 	mips64ClangCflags = append(mips64Cflags, []string{