[RISC-V] Fix MarshalStructAsLayoutSeq

[clamp03]

• Fix MarshalStructAsParam_AsSeqByValFixedBufferClassificationTest
• Fix MarshalStructAsParam_AsSeqByValUnicodeCharArrayClassification
  Ex. Argument in struct { int a, int b, float c} type should be passed with two integer registers (not one integer register and one float register).

Part of #84834
cc @wscho77@HJLeee@JongHeonChoi@t-mustafin@alpencolt@gbalykov@tomeksowi

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Issue Details

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• Fix MarshalStructAsParam_AsSeqByValFixedBufferClassificationTest
• Fix MarshalStructAsParam_AsSeqByValUnicodeCharArrayClassification
  Ex. Argument in struct { int a, int b, float c} type should be passed with two integer registers (not one integer register and one float register).

Part of #84834
cc @wscho77@HJLeee@JongHeonChoi@t-mustafin@alpencolt@gbalykov@tomeksowi

Author:	clamp03
Assignees:	-
Labels:	area-CodeGen-coreclr
Milestone:	-

[clamp03]

@jakobbotsch Could you take a look at this PR? Thank you so much.