CV32E40Pv2 SIMD 6-bit Unsigned Immediate + Renamed SIMD GAS Tests

Created by: NandniJamnadas

• Renamed GAS tests from cv-[instruction name] to cv-simd-[instruction name].
• Created a 6-bit unsigned immediate 'b8' for SIMD.
• Updated SIMD instructions from signed to unsigned and their corresponding tests, instructions included are:
  • cv.cmpgeu.sci[.h, .b]
  • cv.cmpgtu.sci[.h, .b]
  • cv.cmpleu.sci[.h, .b]
  • cv.cmpltu.sci[.h, .b]
  • cv.dotup.sci[.h, .b]
  • cv.maxu.sci[.h, .b]
  • cv.minu.sci[.h, .b]
  • cv.sdotup.sci[.h, .b]
  • cv.shuffle.sci.h
  • cv.shufflei0.sci.b
  • cv.shufflei1.sci.b
  • cv.shufflei2.sci.b
  • cv.shufflei3.sci.b